A13A-0202
In-situ observations of high-latitude atmospheric turbulence
Sounding rocket measurements have provided some of the most detailed observations of the small-scale
response of the neutral lower thermosphere to magnetospheric energy input in the auroral zone. In January
and February 2007, a series of such launches were carried out at Poker Flat, Alaska, during substorm
conditions. The rocket measurements provided wind profiles and the north-south gradients in the winds, as
well as detailed in situ measurements of the electric fields, electron densities, particle energies, and neutral
densities, and temperatures. In addition, we were able to detect the development of atmospheric turbulence
at 80 km through analysis of the TMA reinjection bag. The atmospheric turbulence develops soon after the
cloud forms, and proceeds from Navier-Stokes through Kraichnan turbulence in the most diffuse
observations towards the end of the observations.
http://web.presby.edu/~wanliss
A13A-0203
CPC Experimental MJO Forecast Tools Using Operational GFS and CFS Data
CPC is actively developing additional MJO-related forecast tools to aid its operational mission for the monitoring, assessment, and prediction of the MJO and its associated impacts. We present recent work for products based on data from the Global Forecast System (GFS) and Climate Forecast System (CFS) forecast models developed at the National Centers for Environmental Prediction (NCEP). We apply the Wheeler and Hendon (2004) MJO identification methodology to the realtime operational GFS (control and ensemble) and CFS forecast data. Although this approach for identification of the MJO is well-established, it has only been recently that it has been applied to dynamical model data at several global operational centers. We describe our approach, modifications necessary for practical realtime operational considerations, and initial verification statistics for both the GFS and CFS data. Application of the new tools to the CPC weekly MJO update and Experimental Global Tropics Benefits/Hazards Assessment and collaboration with other operational centers as part of the US CLIVAR MJO working group are also discussed.
A13A-0204
CFC Destruction of Ozone - Major Cause of Recent Global Warming!
There has been a lot of discussion about global warming. Some say anthropogenic carbon dioxide (CO2)
emissions caused the earth to warm. Others say there is no abnormality at all, that it is just natural warming.
As you will see from the data presented and analyzed, a greater than normal warming did occur in recent
times but no measurements confirm an increase in CO2, whether anthropogenic or natural, had any effect on
global temperatures. There is however, strong evidence that anthropogenic emissions of
chlorofluorocarbons (CFCs) were the major cause of the recent abnormal warming. CFCs have created both
unnatural atmospheric cooling and warming based on these facts: CFCs have destroyed ozone in the lower
stratosphere/ upper troposphere causing these zones in the atmosphere to cool 1.37°C from 1966 to
1998. This time span was selected to eliminate the effect of the natural solar irradiance (cooling-warming)
cycle effect on the earth's temperature. The loss of ozone allowed more UV light to pass through the
stratosphere at a sufficient rate to warm the lower troposphere plus 8-3/4" of the earth by 0.48°C
(1966 to 1998). Mass and energy balances show that the energy that was absorbed in the lower
stratosphere and upper troposphere hit the lower troposphere/earth at a sustainable level of 1.69 ×
10 18 Btu more in 1998 than it did in 1966. Greater ozone depletion in the Polar Regions has caused these
areas to warm some two and one-half (2 1/2) times that of the average earth temperature -1.2°C
versus 0.48°C. This has caused permafrost to melt, which is releasing copious quantities of methane,
estimated at 100 times that of manmade CO2 release, to the atmosphere. Methane in the atmosphere slowly
converts to CO2 and water vapor and its release has contributed to higher CO2 concentrations in the
atmosphere. There is a temperature anomaly in Antarctica. The Signey Island landmass further north,
warmed like the rest of the Polar Regions; but south at Vostok, there has been a cooling effect. Although the
cooling at Vostok needs to be analyzed in more detail, because of the large ozone hole there, black body
radiation from Vostok, some 11,400 feet above sea level, to outer space is most likely the cause. Especially,
since this phenomenon occurred over the same period that stratospheric ozone destruction took place.
Chlorofluorocarbon destruction of stratospheric ozone can be correlated nicely with both the cooling and
warming temperature anomalies seen over the time span from 1966 to 1998 and compared to actual
temperature measurements, the ozone signature for global warming is the closest of the five signature
impacts developed by the IPCC. Further,the "greenhouse signature" is not seen at all. One can account for
most, if not all, of the 0.48°C rise in earth's temperature from 1966 to 1998 with the additional UV light
that hit the earth due to ozone destruction in the upper atmosphere.
http://omsriram.com/GlobalWarming.htm
A13A-0205
Global atmosphere/ocean structures associated with the Indian monsoon droughts
This study examines the global atmosphere/ocean structures associated with the Indian monsoon droughts. We analyzed long-term (1948-now) observations of SST, precipitation, sea level pressure, air temperature, winds, Palmer drought index and soil moisture. The life cycle of each drought event is studied in detail. Special attention is paid to the differences between strong events and weak events. Detailed results will be presented at the conference.
A13A-0206
Global atmosphere/ocean structures associated with the African monsoon droughts
This study examines the global atmosphere/ocean structures associated with the African monsoon droughts. We analyzed long-term (1948-now) observations of SST, precipitation, sea level pressure, air temperature, winds, Palmer drought index and soil moisture. The life cycle of each drought event is studied in detail. Special attention is paid to the differences between strong events and weak events. Detailed results will be presented at the conference.
A13A-0207
PBL dynamic measurements with new compact long range wind Lidar WINDCUBE™ WLS70
The WindCube™ WLS70 is a new generation wind Lidar developed by LEOSPHERE for meteorological applications. The Lidar is derived from the commercial WindCube widely used for autonomous and very accurate short range measurements by the wind industry. It has been modified increasing the range up to 4 km and can even detect cirrus at 8km. First results of the measurement campaign which took place in Orsay, France in August 2008 put in evidence both vertical wind speed and atmosphere structure (PBL height , clouds top and base) derived from Lidar data with good time resolution (30s per profile), good range resolution (50m from 100m to 4000m), and good velocity resolution (0.2m/s). These measurement data play a key role in many meteorological applications, and can be used as input for forecast mathematical models.
A13A-0208
A multi-sensor, three-dimensional analysis of San Juan Mountain snowpack for modeling Rio Grande headwater streamflow
In the southwest United States, the majority of the usable water resources come from melted snow in the Rocky Mountains. Specifically, in New Mexico, the San Juan Mountains in southern Colorado contribute much of the snowpack that forms spring and summer river flows in the tributaries of the Rio Grande. The analysis of mountain snowpack is often done with a combination of ground-based instruments and remote sensing instruments on orbiting platforms. Terrain and weather issues make continuous, accurate measurement of water content difficult as it is impractical to take a multitude of ground measurements to attain information on snow-covered area (SCA) and snow-water equivalent (SWE). A project is underway to use established techniques to determine sub- pixel resolution of SCA for an eight-year dataset from 2000 to 2008. Archived and live satellite data from NASA's Moderate Resolution Imaging Spectro-Radiometer (MODIS) will be the primary source of remote sensing information for determining SWE through the early, peak and late season snowpack found in southern Colorado. The final results for SWE will be compared with river gauge data obtained from the US Geological Survey will determine an efficiency rating of snowpack to usable freshwater in the Rio Grande, in addition to lag time between peak snowpack and peak river discharge.
A13A-0209
Estimating the true amplitude of the Southern Hemisphere storm tracks using COSMIC data
The true amplitude of the Southern Hemisphere storm tracks is still poorly known, as the NCEP-NCAR and ECMWF ERA40 reanalyses differ signifiantly in this measure. The difference is mainly due to the lack of conventional observations in the Southern Hemisphere as well as the different ways the two reanalyses assimilate satellite radiance observations. In this work, the true amplitude is investigated using the recently available COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) radio occultation dataset. The COSMIC dataset has the advantage of having global coverage (about 2000 profiles per day) with similar biases and errors in both hemispheres. Furthermore, it is not assimilated in the reanalysis yet, thus it can be treated as an independent data source to validate the reanalysis. Daily geopotential height on a 2.5*2.5 deg lon-lat grids from Aug 2006 to Apr 2008 is obtained by analysing COSMIC profiles using the Cressman analysis method, and its 24-hour difference filtered variance is computed to represent the strength of the baroclinc waves. The ratio of the amplitude of the variance averaged over the Southern Hemisphere to that in the Northern Hemisphere is regarded as a value close to the true inter-hemisphere ratio. Comparing the ratio based on the COSMIC dataset with that based on the reanalysis, and assuming that the reanalysis is reliable in the Northern Hemisphere, the bias of the reanalysis in the Southern Hemisphere can be inferred. In this way, it is found that the amplitude of the Southern Hemisphere storm tracks in the NCEP-NCAR reanalysis is significantly biased low by about 30% at 300mb. The amplitude in the ECMWF ERA40 is much closer to that inferred from COSMIC observations. This work gives the first quantitative estimate of the true amplitude of the Southern Hemisphere storm tracks made independent of numerical model outputs. In addition to exploring the biases in the reanalyses, our results can also be applied to assess whether the storm track amplitudes in GCM simulations are realistic or not.
A13A-0210
The decline of fog, mist and haze in Europe during the last 30 years: a warming amplifier?
Since the 1970s, European temperatures have risen by ~0.5°C per decade. This rate is much faster than that of global mean temperatures (≈ 0.18°C/decade) and mean temperatures over land (≈ 0.27°C/decade) during the same period. Current regional climate models fail to simulate this rapid evolution. The surface solar radiation increase since the 1980s is thought to have contributed to this additional warming, but its link with temperature trends has not been quantified so far. Here we show that significant changes in low-level atmospheric phenomena such as fog, mist and haze may have largely contributed to this recent climate evolution in Europe. From the analysis of a large multi-decade set of surface horizontal visibility data, we show that the frequency of these phenomena strongly declined during the last three decades all over Europe and for all seasons. The improvement in air quality during this period is a possible cause, as the spatial pattern of this decline is correlated to that of pollutant emission reductions in Europe. Then, using an original statistical methodology linking local visibility changes with temperature changes, we show that this decline could have contributed on average to about 20% of recent daytime warming, and to more than 50% in parts of Eastern Europe. These results emphasize the essential role of natural and man-induced atmospheric boundary-layer processes in regional climate variations.
A13A-0211
Remote Climate Forcings of Jamaica's Mid-Summer Dry Spell and Vegetative Response
The seasonal cycle of the Intra-Americas Sea Mid Summer Dry Spell (MSD) is characterized by a bimodal rainfall season with peaks occurring in the late spring and late summer. While the MSD is a permanent feature it undergoes interannual variability. Jamaican farmers have verified that the perceived MSD variability represents a significant obstacle to their cropping strategies, especially in July. Rainfall in July over Jamaica is influenced by the El Nino Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). During warm year (0) ENSO events rainfall is reduced while the warm year (1) ENSO events promote wetter than normal conditions during the Jamaican MSD. Early Spring NAO phase values tend to correspond negatively to the upcoming Jamaican MSD rainfall. Together, the ENSO warm phase year (0) and a strong NAO during the early spring results in a constructive interference pattern that greatly inhibits Jamaican MSD rainfall. The impact of the MSD pattern can be discerned via a lagged vegetation response observed through a similar bimodal pattern of the Jamaican land surface normalized difference vegetation index (NDVI). Understanding the NDVI response to the MSD allows the ability to produce future vegetative stress related scenarios upon upcoming MSD signals for Jamaican farmers.
A13A-0212
The boreal springtime formation of the Somali Jet: dynamics of its seasonal evolution and diurnal cycle
While the Somali Jet has been widely studied during the boreal summer months (JJAS), the early stages of the jet's formation in April and May are not as well documented or understood. Riddle and Cook (2008) noted that starting in mid-April, a strong southerly cross-equatorial jet is present at 925 hPa along the coast of East Africa. This preliminary stage in the development of the Somali Jet is distinct from the fully-formed Somali Jet in that 1) it is confined to a narrow region along the coast and 2) it consists solely of a meridional branch which terminates over the Horn of Africa. In this study, we examine the dynamics associated with the springtime jet's seasonal evolution and diurnal cycle using the NCEP II reanalysis and a high-resolution regional model simulation. A momentum budget analysis based on the NCEP II climatology shows that the cross-equatorial flow along the east African coast is governed by the large-scale pressure difference between northern and southern hemispheres over the Arabian Sea basin. This north-south pressure gradient becomes positive in early March and increases gradually throughout the boreal spring, primarily due to strong surface heating over the Asian landmass to the north, and cooling over southern Africa. However, the springtime coastal jet does not acquire a jet-like structure until mid-April when the zonal land/sea pressure gradient between the Indian Ocean and the African continent disappears, eliminating the previously strong zonal (onshore) component to the flow. The zonal branch of the Somali jet forms over the Arabian Sea in June, when depressions over India and Africa merge to form the zonal monsoon trough. The timing of the zonal branch formation is coincident with the onset of the Indian monsoon. The diurnal cycle of the springtime Somali Jet is examined using a high resolution regional climate model and found to be controlled primarily by day/night changes in surface friction. This study provides a physical understanding of the dynamics controlling the formation of the Somali Jet in the boreal springtime, and lays the groundwork for further investigation into, for example, its interannual variability.
A13A-0213
The Influence of Eastern Indian Ocean Convection on Wintertime Asian Precipitation
We investigate the regional influence of tropical convection in the eastern Indian Ocean during the boreal cold season, both in terms of the mean response and in the context of the seasonally-evolving background flow. Wintertime tropical convection in the Indian Ocean has been linked to large changes in precipitation over Southwest Asia, including both multi-year drought and MJO-driven short-term flooding episodes. We analyze the regional influence with both observational analysis and modeling experiments. The modeling experiments utilize a modified version of the NCAR CAM 3.1, where we modify the calculation of diabatic heating in the model to create an enhanced area of tropical convection, with all other aspects of the model left to freely evolve. This is similar to linear modeling experiments with specific diabiatic heating forcing, but allows the response to evolve in a fully nonlinear fashion, with direct simulation of moist processes and precipitation. The analysis shows that enhanced tropical oceanic convection forces strong subsidence over SW Asia by generating a Gill-type Rossby wave response that intersects with the jet -- the resulting temperature advection is balanced by subsidence. The reverse occurs with suppressed tropical convection. There is considerable similarity between the patterns of interannual variability and intraseasonal (MJO) variability, but with some significant differences in extent and latitudinal position of the ocean convection, which we examine with both an idealized Gill-type model and a series of modified GCM experiments. Month-by-month analysis suggests some limitations of the GCM, apparently due to an imperfect representation of the jet in some months, which we further analyze in GCM runs with diabatic heating specified over the whole globe. Finally, we relate our analysis to Jan-Apr 2008, which was another severe drought period for Southwest Asia.
A13A-0214
Impact of Heterogeneous Vegetation Momentum Roughness on Mesoscale Model Dynamics
This study implemented a satellite-derived vegetation aerodynamic roughness and zero plane displacement height dataset in a mesoscale model. The roughness dataset, based on MODIS-derived canopy density at 1 km spatial resolution and 9 day temporal resolution, offers an alternative to standard look-up table values based solely on land class. The model used was the Weather Research and Forecast (WRF) model coupled to the Community Land Model embedded in the Land Information System (LIS), or LISWRF. A 4 day period from June 3 to 7, 2002 was simulated using LISWRF over a domain covering the south central United States. Three different integrations were performed, one using standard look-up table roughnesses, another using the new MODIS-derived roughnesses, and the third using a climatology based on the MODIS dataset. It was found that the heterogeneity contained in the MODIS dataset had significant impact on the simulated momentum, temperature, and moisture fields.
A13A-0215
The EUMETSAT Polar System - Achievements Two Years after Launch of Metop- A
Metop-A, the first of the Metop series of polar-orbiting operational meteorological satellites was launched on
the 19th October 2006. The remaining two satellites in the series will be launched in 2011 and 2015. Metop is
Europe's first polar-orbiting satellite dedicated to operational meteorology. It represents the European
contribution to a new cooperative venture with the United States - the Initial Joint Polar System IJPS -
providing data that is used to monitor our climate and improve weather forecasting. Europe serves the mid-
morning orbit, whereas NOAA will continue to serve the afternoon orbit.
A new generation of European instruments that offer improved remote sensing capabilities to both
meteorologists and climatologists are carried along with a set of "heritage" instruments provided by the
United States. The new European instruments have been respectively developed by ESA (ASCAT, GRAS,
GOME-2), CNES (IASI) and EUMETSAT (MHS) and will offer advanced sounding capabilities, the
measurement of ocean surface wind as well as improved observation of ozone and other trace gases.
Providing unprecedented accuracy in meteorological data, the European contribution will lead to a better
understanding of our climate.
Meteorological "heritage" instruments provided by the United States are part of the complement of American
instruments provided by the National Oceanic and Atmospheric Administration (NOAA) to fly on Metop-A and
-B, and, with the exception of HIRS, also on Metop-C. They are the AMSU-A1 and A2 Advanced Microwave
Sounding Units, the HIRS/4 High Resolution Infrared Sounder and the AVHRR Advanced Very High
Resolution Radiometer. They fly also on the NOAA afternoon satellites (NOAA-18 and NOAA-N').
More than two years after the launch of Metop-A the achievements and perspectives for the Metop series of
satellites will be presented.
http://www.eumetsat.int
A13A-0216
A Nocturnal Boundary Layer Simulation over the ARM-CART Site
The nocturnal boundary layer (NBL) is characterized by strong inversions and weak turbulent motions. It is during this time that low-level jets (LLJs) often form as the winds aloft reach speeds approaching 15-25m/s at levels below 1000m. During the daytime, turbulent mixing quickly damps such organized motion, but at night the surface cooling establishes an inversion which reduces turbulence and allows jets to form uninhibited. A field project over the ARM-CART site during a period of several nights in September, 2007 was conducted to explore the jet evolution. Data was collected from a tower and analyzed for turbulent behavior. With data limited to a single location, however, the full range of NBL behavior is difficult to determine. The Regional Atmospheric Modeling System (RAMS) is therefore used to simulate the ARM-CART NBL field experiment and validated against the data collected from the site. This model was run at high resolution, and is ideal for calculating the interactions among the various motions within the boundary layer and their influence on the surface. The model can provide information throughout the NBL - with a larger domain, a simulation of the NBL can provide information over a large range of locations and heights. In particular, we are interested in the way that the simulated NBL eddies are affected by their height and proximity to the LLJ, and how this compares to the tower results. The eddy sizes that exist in the model are limited by its grid spacing, but a series of smaller, finer nests allow us to study eddy motion at the relevant scales for short periods.
A13A-0217
Dynamical downscaling of Era40 in Norway
A novel approach for downscaling of the Era40 data set has been taken and results from comparison with observations in Norway will be presented. The approach make use of a nudging technique in a stretched global model with the grid focus at (67N, 5W). The effective resolution is three times the one of the Era40, equivalent to about 30km grid spacing in the area of focus. Longer waves are nudged towards Era40 while the short waves are set free to evolve. The comparison to observations incorporate numerous station data points of i) precipitation (#357), ii) temperature (#98) and iii) wind (#10), and the new data set shows large improvements over Era40. The results from daily precipitation show considerably reduction in bias (from 50% to 11%), and a two-fold reduction (-59% to 29%) at 99.9%tile level. The daily temperature bias was reduced by about a degree in most areas, and the RMSE was reduced significantly (from 7.5 to 5.0 except winter). The wind comparison indicated a slight improvement in bias, and significant improvement in RMSE.
A13A-0218
A study of OH imager observed concentric gravity waves near Fort Collins on 11 May 2004
Expanding concentric rings of gravity waves were observed on the night of 11 May 2004 by the all-sky OH imager at Yucca Ridge Field Station (40.7°N, 104.9°W) near Fort Collins, Colorado. The pattern was observed for about 1.5 hours, with the rings encompassing nearly 360° for the first 30 minutes. The centers of the rings were observed at the geographic locations of two convective plumes. We measure the horizontal wavelengths and periods of these gravity waves as functions of both radius and observation time. The observations compare favorably with predictions from a ray-tracing program using the internal gravity wave dispersion relation with assumed zero wind. Since all the 5 events of concentric patterns among 760 nights of image were observed in May or late August/early September, we hypothesize that the weak mean background zonal wind near equinoxes is a necessary condition for gravity waves excited from convective overshoots near the tropopause to be observed as concentric rings in the OH layer.
A13A-0219
Using z-score and threshold parameters to improve SSM/I data
The National Oceanic and Atmospheric Administration's National Climatic Data Center has archived and served the Defense Meteorological Satellite Program Special Sensor Microwave/Imager (SSM/I) data from the F-10, F-11, F-13, F-14, and F-15 platforms since August 1993. Passive microwave satellite measurements from SSM/I have been used to generate climate products in support of national and international programs. A normalized anomaly (z-score) for each footprint temperature value was calculated by subtracting the value with the corresponding monthly one degree grid climatological mean and dividing it by the associated climatological standard deviation. The SSM/I climatological period of record or population data covers data from all the platforms from August 1993 to present. Threshold checks were also used to detect radiance, temporal and geolocation values that were out of the expected ranges. As part of this effort, the SSM/I Temperature Data Record (TDR) and Sensor Data Record (SDR) data sets have been reprocessed as network Common Data Form (netCDF) orbit files. The application of z-scores and threshold parameters in the form of quality flags has vastly improved the quality of the SSM/I TDR/SDR period of record. This effort has helped to preserve and increase the data maturity level of the longest satellite passive microwave period of record.
A13A-0220
Non-equilibrium effects in atmospheric characteristic oscillations due to radiation balance
Nowadays researches on global change of climate are faces the challenge of insufficient development of open system theory. In this connection the problem of energy and entropy exchange process between solar radiation and atmospheric gas influence on atmospheric dynamics in the frames of non-equilibrium thermodynamics was studied in this work. For this purpose the equations of flow [fluid] dynamics for interacting medium – gas and radiation – with taking into account the entropy production in atmosphere and its exchanging between gas and radiation were used in this work. Dispersion relation numerical analysis of atmospheric gravity waves (AGWs) in non-equilibrium atmosphere was carried out. It has been established that the spectra in the daytime hours shifts on high-frequency region in comparison with nighttime spectra. This difference can reach several percent in certain atmospheric regions. For the spectrum of the equilibrium model of the atmosphere the difference between the daytime and nighttime spectra makes up several fractions of percent. A comparison of the theoretical calculations of AGWs spectrum with observations confirmed the availability of non-equilibrium effects in the AGWs spectral composition. In particular, that concerns of Antarctic data results gave the difference is about 4 percent, Almaty data results ranges between 1.3 – 6 per cent in depends of season. Investigation of wave disturbances on sunset and sunrise periods of time shows that there is a tendency for low frequency region at evening-time spectra and high frequency region at morning- time spectra.
A13A-0221
Estimation of the impacts of different homogenization approaches on the variability of temperature series in Catalonia (North Eastern-Spain), Andorra and South Eastern - France. An experiment under the umbrella of the HOME-COST action.
The almost unanimously accepted fact of climate change has brought many scientists to investigate the seasonal and interannual variability and change in instrumental climatic records. Unfortunately, these records are nearly always affected by homogeneity problems caused by changes in the station or its environment. The European Cooperation in the Field of Scientific and Technical Research (COST) is sponsoring the action COST-ES0601: Advances in homogenisation methods of climate series: an integrated approach (HOME), which aims amongst others to investigate the impacts of different homogenisation ap-proaches on the observed data series. In this work, we apply different detection/correction methods (SNHT, RhTest, Caussinus-Mestre, Vincent Interpolation Method, HOM Method) to annual, sea-sonal, monthly and daily data of a multi-country quality controlled dataset (17 stations in Catalonia (NE Spain); 3 stations in Andorra and 11 stations in SE France). The different outputs are analysed and the differences in the final se-ries studied. After this experiment, we can state that – although all the applied methods im-prove the homogeneity of the original series – the conclusions extracted from the analysis of the homogenised annual, seasonal, monthly data and extreme indices derived from daily data demonstrate important differences. As an exam-ple, some methods (SNHT) tend to detect fewer breakpoints than others (Caussinus-Mestre). Even if metadata or a pre-identified list of breakpoints is available, the correction factors calculated by the different approaches differ both in annual, seasonal, monthly and daily scales. In the latter case, some methods like HOM – based on the modelling of a candidate series against a reference series – present a richest solution than others based on the mere in-terpolation of monthly factors (Vincent Method), although the former are not al-ways applicable due to lack of good reference stations. In order to identify the best performing method (or suite of methods) COST-HOME action is conducting an intensive testing of the different homogenisation methods over simulated, surrogated and real series. At the end of the action (2011), we expect to present a significant contribution to a better evaluation of seasonal and interannual variability and change.
A13A-0222
Performance of an Interpolated Stochastic Weather Generator in Czechia and Nebraska
Met&Roll is a WGEN-like parametric four-variate daily weather generator (WG), with an optional extension allowing the user to generate additional variables (i.e. wind and water vapor pressure). It is designed to produce synthetic weather series representing present and/or future climate conditions to be used as an input into various models (e.g. crop growth and rainfall runoff models). The present contribution will summarize recent experiments, in which we tested the performance of the interpolated WG, with the aim to examine whether the WG may be used to produce synthetic weather series even for sites having no meteorological observations. The experiments being discussed include: (1) the comparison of various interpolation methods where the performance of the candidate methods is compared in terms of the accuracy of the interpolation for selected WG parameters; (2) assessing the ability of the interpolated WG in the territories of Czechia and Nebraska to reproduce extreme temperature and precipitation characteristics; (3) indirect validation of the interpolated WG in terms of the modeled crop yields simulated by STICS crop growth model (in Czechia); and (4) indirect validation of interpolated WG in terms of soil climate regime characteristics simulated by the SoilClim model (Czechia and Nebraska). The experiments are based on observed daily weather series from two regions: Czechia (area = 78864 km2, 125 stations available) and Nebraska (area = 200520 km2, 28 stations available). Even though Nebraska exhibits a much lower density of stations, this is offset by the state's relatively flat topography, which is an advantage in using the interpolated WG. Acknowledgements: The present study is supported by the AMVIS-KONTAKT project (ME 844) and the GAAV Grant Agency (project IAA300420806).
A13A-0223
Dynamical-statistical Forecasting of Seasonal Air Temperature Over European Part of Russia
The aim of the present study is to improve prediction of seasonal surface air temperature using outputs of 7 GCMs from Russia, Korea, USA, and Japan. Geographical regions in European part of Russia with identical pattern of variability of monthly air temperature were identified using one objective classification method. Averaged over each identified regions air temperatures from NCEP/DOE reanalysis dataset were used as a predictant matrix. Modified "Perfect Prognosis" method was served as forecasting approach. Consistent spatial patterns between forecasted by different models H-500 fields and smoothed reanalysis air temperature were found. EOF analysis was applied to these informative areas separately for negative and positive correlation patterns. The 1st EOF for each model corresponded to maximal ~80% explained variance of H-500, and the convergence of EOFs for positive correlation areas was higher then that for negative. Predictor data set was created selecting only 1st EOFs of H-500 of 7 input models. Stepwise multiple regression technique allowed selecting optimal two predictor variables. The results demonstrated improved forecast skill compared to separate model forecasts and multi-model mean forecasts. This study has been supported by RFBR grants 07-05-00740, 07-05-13591.
A13A-0224
Entropy Constraints on Vertical Heat Transport and Structures
Vertical heat transport by evaporation and condensation is a key process in transferring energy from the surface of the Earth to the atmosphere. Although this process has been studied for a long time, thermodynamic constraints on this process and on the vertical structures of the atmosphere are still poorly understood and quantified. In this work, we use a simple 1D vertical energy-entropy climate model to investigate this issue. Especially, we explore the roles of the entropy-rated constraints in determining vertical heat transport and atmospheric vertical structures. The sensitivities of the vertical distributions of atmospheric temperature, the energy and entropy fluxes to the variation of solar radiation are also discussed.
A13A-0225
Modern Era Retrospective-analysis for Research and Applications (MERRA) Data and Services at the GES DISC
The Modern Era Retrospective-analysis for Research and Applications (MERRA) dataset is a NASA 30 year (1979 - 2007) reanalysis using the Goddard Earth Observing System Data Assimilation System, Version 5 (GEOS-5). The project, run out of NASA's Global Modeling and Assimilation Office at Goddard Space Flight Center, provides the science and application communities with a state-of-the-art global analysis with emphasis on improved estimates of the hydrological cycle over a broad range of weather and climate time scales. MERRA products are generated as a long-term synthesis that places the NASA EOS suite of observations in a climate context. The MERRA analysis is performed at a horizontal resolution of 2/3 x 1/2 degrees and at 72 levels, extended 0.01 hPa. Hourly, two-dimensional diagnostic fields are at the native horizontal resolution. Other products are available on a coarser horizontal grid with resolutions of 1.25 x 1.25 and 1.0 x 1.25 degrees. Daily and monthly MERRA products (with others to follow later) are archived and distributed by the Goddard Earth Sciences Data and Information Services Center (GES DISC) through its Modeling DISC Web (MDISC) portal. Multiple data access methods and services are available for MERRA data through MDISC: (1) Mirador offers a quick, comprehensive search of MERRA and all GES DISC archived data holdings, allowing searches on keywords, location names or latitude/longitude box, and date/time, with responses within a few seconds. (2) Giovanni is a GES DISC developed Web application that provides data visualization and analysis online. Giovanni features popular visualizations such as latitude- longitude maps, animations, cross sections, profiles, time series, etc. and some basic statistical analysis functions such as scatter plots and correlation coefficient maps. Users are able to download results in several different formats, including Google Earth. (3) On-the-fly parameter subsetting of data within a spatial/temporal window is provided through a simple "select and click" Web page. (4) MERRA data are also available via OPeNDAP, GrADS Data Server (GDS) and can be converted to netCDF "on the fly". Detailed MERRA data access information is available at the MDISC portal: http://disc.gsfc.nasa.gov/MDISC
A13A-0226
Sensitivity of Simulated Convective Storm Outflows and Cold Pools to Environmental Parameters
Using results from a large set of three-dimensional cloud resolving model simulations, we investigate the
sensitivity of storm outflows, downdrafts, and cold pools to background environmental conditions. The
dominant right-moving storm in each of over 200 unique experiments is analyzed, and its properties
averaged during the second hour of 2 h simulations, to assess the general relationships between storm
outflow characteristics and environmental parameters.
The strongest surface wind gusts and largest areas of outflow are produced when convective available
potential energy (CAPE) and bulk tropospheric wind shear are large, these being environmental conditions
that are hallmarks of vigorous, organized convection. Strong winds are also more widespread when the
atmospheric precipitable water (PW) is large, which permits greater production of precipitation aloft, and
when the lifted condensation level (LCL) is raised, allowing increased evaporation of falling hydrometeors in
the downdraft. Storm cold pool temperature deficits and areal coverages exhibit more complicated
relationships, but cold pools are generally larger and relatively colder in warm environments (i.e., high PW)
and when CAPE is large. These findings help clarify the environmental conditions that influence the surface
"sensible weather" produced by deep, moist convection.
http://space.hsv.usra.edu/COMPASS/
A13A-0227
U.S. Department of Agriculture UV-Monitoring and Research Program and Integrated Crop Modeling Activity
The US Department of Agriculture's UV Monitoring and Research Program (USDA-UVMRP) has monitored
surface solar irradiance in the UV and visible regions of the spectrum for over a decade. Measurements of
spectral irradiance have been made at 34 sites in the US as well as one site in New Zealand and two in
Canada. These measurements are complemented by readings of the erythemally weighted irradiance and
Photosynthetically Active Radiation. The purpose of the network is to supply datan used to assess the risk to
agriculture of variations in incident solar radiation. A robust climatology of these data has been constructed,
and it serves a multitude of requests from the agricultural, medical and industrial communities. The USDA-
UVMRP at Colorado State University is also the home of the Center of Remote Sensing and Modeling for
Agricultural Sustainability (CRSMAS). The purpose of CRSMAS is twofold: first, to evaluate response of
plants, forests, ecosystems, and animals to UV-B and other climate stress factors; and second, to develop an
Integrated Agricultural Impact Assessment System. The Integrated Agricultural Impact Assessment System
couples a state-of-the-art mesoscale region Climate-Weather Research and Forecasting model (CWRF) with
the most comprehensive crop growth models to study climate-crop interactions. The data from the USDA-
UVMRP network is used in conjunction with data assimilated from various satellite platforms as input into the
CWRF model. A overview of the UVMRP network, its instrumentation and climatological results will be
presented as well as an example of the application of the Integrated Impact Assessment System to a study of
the response of cotton yields to climate stresses during the 1979-2005 period.
http://uvb.nrel.colostate.edu/UVB/
A13A-0228
Simulation of Extreme Wind and Precipitation Patterns Associated with a Squall Line Passage in Southern Ontario on August 2, 2006
In the evening of August 2, 2006, a squall line moved across the southern Ontario cottage country, Canada, from northwest to southeast, spawning at least 8 tornadoes, including two F2 confirmed touchdowns. The damage was extensive, cutting electricity power to more than 175,000 customers and flooding many homes. Some areas experienced more than 100 mm of rainfall. There was extensive wind damage from strong winds and wind gusts of 80 to over 100 km per hour. Using the Canadian operational weather forecast model, GEM-LAM (Global Environmental Multiscale – Limited Area Model), we have simulated the squall line event, in an attempt to highlight at least some of the major mechanisms that produced extreme winds and precipitation associated with the storm. For wind gusts, we employed the physically-based diagnostic parameterization scheme developed by Brasseur (2001), and following Goyette et al. (2003), that allows bringing down to the surface of high momentum air flow in the upper part of the planetary boundary layer. With this parameterization, the model produces results that are within 10-20% of the observed wind gusts. In spring of this year (2008), the cloud microphysical scheme in the model was replaced by the Milbrandt-Yau scheme. For the simulation of the August event, the model produces rainfall rates and accumulated amounts in a range consistent with the observation over the affected region.
A13A-0229
Dynamics of the Low-Level Westerly Jet Over West Africa
As identified earlier, a low level westerly jet forms over West Africa from June until mid October. This jet plays a major role in transporting moisture into the Sahel during the summer. Also, the strong horizontal and vertical wind shears associated with the jet over coastal West Africa are very important to the summer circulation in the area. Since only a few studies have been done on this low level jet, further understanding is needed. In our paper, the structure, seasonality, diurnal cycles, and dynamics of the low-level westerly jet over West Africa are investigated in the high resolution ERA40 reanalysis, with the lower resolution NCEP/DOE AMIP-II reanalysis added for reference. Five stages of jet development are identified in the daily ERA40 climatology. At 925 hPa, westerly winds start over the ocean in early June at 8°-11°N, between 13°W and the coast of West Africa. Westerly winds expand westward to 22°W during late June into July. From late July to early September, the jet reaches a maximum in the region of 13°-30°W and 9°-11°N with wind speeds about 3-4 m/s in the 26-year NCEP2 climatology and 5-6 m/s in the 44-year ERA 40 climatology. The jet decreases and retreats eastward to 25°W during mid September. From late September to mid October, the westerly winds over the ocean strongly decrease to 1-2 m/s and the jet disappears. The formation of the jet accompanies the development of a westward extension of the continental thermal low over the ocean. A local low-level low is formed when the jet is at its maximum. Study of the vertical structure of the westerly jet shows that in the ERA reanalysis, the jet peaks at 925 hPa over the ocean, which is lower than the zonal wind center associated with the West African monsoon at the same latitudes. Above 700 hPa, the winds change to easterly. At low levels, distinguished from the monsoon flow, the jet does not have a strong meridional wind component. Also, being located within the ITCZ, the jet region exhibits strong vertical convection and low-level convergence. In the 6-hourly ERA40 climatology, the westerly jet shows a weak diurnal cycle with strongest winds at 17 hr local time and weakest at local 11 hr. The amplitude of the diurnal cycle is about 1-2 m/s. Momentum budget analyses are applied to the regions of the jet, the West Africa monsoon, and the transition between them. The results show that in the jet region the zonal winds are nearly geostrophic. As the Coriolis force is a little larger than the pressure gradient force, the resultant ageostrophic winds are positive and the jet is supergeostropic. In both the transition and monsoon regions, the meridional pressure gradient is about as twice large as in jet region and cannot be balanced by the Coriolis force, so the actual wind speeds are subgeostrophic. In the jet region during July to September, weak vertical wind shears tend to increase the westerly wind speeds by vertical advection while ascending vertical winds tend to weaken the jet. Mechanisms that maintain the thermal low extension are also discussed.
A13A-0230
A map-based South Pacific rainfall climatology
The lives of more than four million people that reside in the South Pacific are greatly affected by rainfall variability. This region is subjected to large rainfall anomalies on seasonal timescales due to tropical cyclone occurrences, ENSO activity, and the AAO. Regional climate anomalies are also dictated by the IPO on multi- decadal scales that alter the motions of large-scale circulation features like the South Pacific Convergence Zone (SPCZ). Strong climate change impacts are anticipated for this region, so gauging the severity of rainfall variations that can occur are paramount for implementing appropriate climate change adaptation measures. Lack of historical rainfall records and documentation of other climate data hinders our current understanding of South Pacific climate variability. Climate data rescue activities are currently aimed at recovering, archiving, and digitising this information to rectify this issue. This research aims to examine the rainfall database administered by the Island Climate Update (ICU) project, which is contributed to by all Pacific Island national meteorological services (NMS), Meteo-France (New Caledonia and French Polynesia), NIWA (New Zealand), NOAA (USA), the IRI (USA), and the Bureau of Meteorology (Australia). Monthly rainfall totals for all stations in the ICU database were assessed, and allowed construction of master rainfall chronologies for all or portions of the major South Pacific Island nations. Climatic norms were then calculated over common time periods, and monthly-resolved rainfall anomaly maps for the South Pacific covering 1951-2008 were undertaken. Immediate benefits of this exercise have pointed out holes in the rainfall network that can be specifically targeted for data rescue in the near future, which can be achieved by providing financial assistance to Pacific Island NMSs. In addition, there is ample scope to extend the rainfall anomaly map time series into the early 1900s using a spatially degraded data set which can be supplemented with subsequent data rescue operations. This map-based time series will also allow us to assess the value of generating a rainfall-based SPCZ reconstruction. We feel this effort could usefully extend the historical documentation of the SPCZ motions that are currently offered by satellite measurements, and complement other historical reconstructions of this major circulation feature.
A13A-0231
Low-frequency variability of the Indian Monsoon-ENSO relation and the Tropical Atlantic: The 'weakening' of the '80s and '90s
The Indian Monsoon-El Nino Southern Oscillation (ENSO) relationship, according to which a drier than normal monsoon season precedes peak El Nino conditions, weakened significantly during the last two decades of the 20th century. In this work an ensemble of integrations of an Atmospherical General Circulation Model (AGCM) coupled to an ocean model in the Indian basin and forced with observed sea surface temperatures (SSTs) elsewhere is used to investigate the causes of such a weakening. The observed interdecadal variability of the ENSO-Monsoon relationship during the period 1950-1999 is realistically simulated by the model and a dominant portion of the variability is associated to changes in the tropical Atlantic SSTs in boreal summer. In correspondence to ENSO, the tropical Atlantic SSTs display negative anomalies south of the Equator in the last quarter of the 20th century and weakly positive anomalies in the previous period. Those anomalies in turn produce heating anomalies which excite a Rossby wave response in the Indian Ocean in both the model and in reanalysis data, impacting the time-mean monsoon circulation. The proposed mechanism of remote response of the Indian rainfall to tropical Atlantic sea surface temperatures is further tested forcing the AGCM coupled to the ocean model in the Indian basin with climatological SSTs in the Atlantic Ocean and observed anomalies elsewhere. In this second ensemble the ENSO-Monsoon relation is characterized by a stable and strong anticorrelation through the whole second half of the XX century.
A13A-0232
Influences of ENSO on North Atlantic Climate and Implications for Long-Range Forecasting
The influence of the El-Niño Southern Oscillation on extratropical climate is established and well documented, especially for the Pacific basin and the North American region. The more remote influence on North Atlantic and Western European climate is still under debate. This work uses observational and model datasets spanning the last century in an attempt to quantify the potential effects of La Niña on the Atlantic-European sector. The analysis examines La Niña teleconnections in different seasons, with focus on summer (including the influence on the probability of extreme summers), and highlights the implications of these teleconnections for long-range forecasting.
A13A-0233
The Response of an Idealized Squall Line to Increases in Atmospheric Temperature With Constant Relative Humidity
Extreme precipitation events are known to be dominated by the amount of moisture advected into the system from surrounding areas rather than local evaporation. Global climate models generally predict that relative humidity will remain largely unchanged as global mean temperature increases. This means that as the climate warms, atmospheric water vapor content will increase. Therefore, it seems reasonable to assume that in a warmer and moister climate a given storm will produce larger precipitation totals. This paper tests that assumption for an idealized squall line using the WRF (Weather Research and Forecasting) regional atmospheric model with a horizonatal resolution of 1km. It is found that storm total rainfall and storm peak rainfall scale with precipitable water when the atmospheric temperature is increased with the relative humidity held constant. However, for a given point on the ground, maximum rainfall accumulation does not exhibit the same scaling property. In fact, changes in maximum point rainfall appear to be unrelated to changes in precipitable water. This is due a strengthening of the internal circulation of the system when the atmosphere becomes warmer and moister. Increased latent heat release intensifies upward motions resulting in stronger outflow from the storm and more rapid advection of the gust front convergence zone. Therefore, although storm peak rainfall increases with increasing precipitable water, rainfall accumulation at a point on the ground does not necessarily do so as the storm passes over the point more rapidly.
A13A-0234
Global atmosphere/ocean structures associated with the South American monsoon droughts
This study examines the global atmosphere/ocean structures associated with the South American monsoon droughts. We analyzed long-term (1948-now) observations of SST, precipitation, sea level pressure, air temperature, winds, Palmer drought index and soil moisture. The life cycle of each drought event is studied in detail. Special attention is paid to the differences between strong events and weak events.