scholarly journals Tropical thin cirrus and relative humidity observed by the Atmospheric Infrared Sounder

2007 ◽  
Vol 7 (6) ◽  
pp. 16185-16225 ◽  
Author(s):  
B. H. Kahn ◽  
C. K. Liang ◽  
A. Eldering ◽  
A. Gettelman ◽  
Q. Yue ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Climate Models ◽  
Temporal Variations ◽  
Ocean Basin ◽  
Specific Humidity ◽  
Future Climate Change ◽  
Effective Diameter ◽  
Regional Variability ◽  
Atmospheric Infrared Sounder

Abstract. Global observations of cloud and humidity distributions in the upper troposphere within all geophysical conditions are critically important in order to monitor the present climate and to provide necessary data for validation of climate models to project future climate change. Towards this end, tropical oceanic distributions of thin cirrus optical depth (τ), effective diameter (De), and relative humidity with respect to ice (RHi) within cirrus (RHic) are simultaneously derived from the Atmospheric Infrared Sounder (AIRS). Corresponding increases in De and cloud temperature are shown for cirrus with τ>0.25 that demonstrate quantitative consistency to other surface-based, in situ and satellite retrievals of cirrus. However, inferred cirrus properties are shown to be less certain for increasingly tenuous cirrus. In-cloud supersaturation is observed for 8–12% of thin cirrus and is several factors higher than all-sky conditions; even higher frequencies are shown for the coldest and thinnest cirrus. Spatial and temporal variations in RHic correspond to cloud frequency while regional variability in RHic is observed to be most prominent over the N. Indian Ocean basin. The largest cloud/clear sky RHi anomalies tend to occur in dry regions associated with vertical descent in the sub-tropics, while the smallest occur in moist ascending regions in the tropics. The characteristics of RHic frequency distributions depend on τ and a peak frequency is located between 60–80% that illustrates RHic is on average biased dry. The geometrical thickness of cirrus is typically less than the vertical resolution of AIRS temperature and specific humidity profiles and thus leads to the observed dry bias, shown with coincident cloud vertical structure obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The joint distributions of thin cirrus microphysics and humidity derived from AIRS provide unique and important regional and global-scale insights on upper tropospheric processes not available from surface, in situ, and other contemporary satellite observing platforms.

scholarly journals Tropical thin cirrus and relative humidity observed by the Atmospheric Infrared Sounder

2008 ◽  
Vol 8 (6) ◽  
pp. 1501-1518 ◽  
Author(s):  
B. H. Kahn ◽  
C. K. Liang ◽  
A. Eldering ◽  
A. Gettelman ◽  
Q. Yue ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Climate Models ◽  
Temporal Variations ◽  
Ocean Basin ◽  
Specific Humidity ◽  
Future Climate Change ◽  
Effective Diameter ◽  
Regional Variability ◽  
Atmospheric Infrared Sounder

Abstract. Global observations of cloud and humidity distributions in the upper troposphere within all geophysical conditions are critically important in order to monitor the present climate and to provide necessary data for validation of climate models to project future climate change. Towards this end, tropical oceanic distributions of thin cirrus optical depth (τ), effective diameter (De), and relative humidity with respect to ice (RHi) within cirrus (RHic) are simultaneously derived from the Atmospheric Infrared Sounder (AIRS). Corresponding increases in De and cloud temperature are shown for cirrus with τ>0.25 that demonstrate quantitative consistency to other surface-based, in situ and satellite retrievals. However, inferred cirrus properties are shown to be less certain for increasingly tenuous cirrus. In-cloud supersaturation is observed for 8–12% of thin cirrus and is several factors higher than all-sky conditions; even higher frequencies are shown for the coldest and thinnest cirrus. Spatial and temporal variations in RHic correspond to cloud frequency while regional variability in RHic is observed to be most prominent over the N. Indian Ocean basin. The largest cloud/clear sky RHi anomalies tend to occur in dry regions associated with vertical descent in the sub-tropics, while the smallest occur in moist ascending regions in the tropics. The characteristics of RHic frequency distributions depend on τ and a peak frequency is located between 60–80% that illustrates RHic is on average biased dry. The geometrical thickness of cirrus is typically less than the vertical resolution of AIRS temperature and specific humidity profiles and thus leads to the observed dry bias, shown with coincident cloud vertical structure obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The joint distributions of thin cirrus microphysics and humidity derived from AIRS provide unique and important regional and global-scale insights on upper tropospheric processes not available from surface, in situ, and other contemporary satellite observing platforms.

Assess 21st century Flash Drought in the United States using high resolution regional climate models

2021 ◽  
Author(s):  
Brandi Gamelin ◽  
Jiali Wang ◽  
V. Rao Kotamarthi
Keyword(s):  
Climate Change ◽  
United States ◽  
Soil Moisture ◽  
Climate Models ◽  
Wrf Model ◽  
The United States ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Regional Variability ◽  
Groundwater Levels

<p>Flash droughts are the rapid intensification of drought conditions generally associated with increased temperatures and decreased precipitation on short time scales.  Consequently, flash droughts are responsible for reduced soil moisture which contributes to diminished agricultural yields and lower groundwater levels. Drought management, especially flash drought in the United States is vital to address the human and economic impact of crop loss, diminished water resources and increased wildfire risk. In previous research, climate change scenarios show increased growing season (i.e. frost-free days) and drying in soil moisture over most of the United States by 2100. Understanding projected flash drought is important to assess regional variability, frequency and intensity of flash droughts under future climate change scenarios. Data for this work was produced with the Weather Research and Forecasting (WRF) model. Initial and boundary conditions for the model were supplied by CCSM4, GFDL-ESM2G, and HadGEM2-ES and based on the 8.5 Representative Concentration Pathway (RCP8.5). The WRF model was downscaled to a 12 km spatial resolution for three climate time frames: 1995-2004 (Historical), 2045-2054 (Mid), and 2085-2094 (Late).  A key characteristic of flash drought is the rapid onset and intensification of dry conditions. For this, we identify onset with vapor pressure deficit during each time frame. Known flash drought cases during the Historical run are identified and compared to flash droughts in the Mid and Late 21<sup>st</sup> century.</p>

scholarly journals The Global Distribution of Supersaturation in the Upper Troposphere from the Atmospheric Infrared Sounder

2006 ◽  
Vol 19 (23) ◽  
pp. 6089-6103 ◽  
Author(s):  
Andrew Gettelman ◽  
Eric J. Fetzer ◽  
Annmarie Eldering ◽  
Fredrick W. Irion
Keyword(s):  
Relative Humidity ◽  
Storm Track ◽  
Satellite Observations ◽  
Atmospheric Infrared Sounder ◽  
Temperature Variance ◽  
Upper Troposphere ◽  
Tropical Tropopause ◽  
Global Coverage ◽  
Higher Temperature

Abstract Satellite data from the Atmospheric Infrared Sounder (AIRS) is analyzed to examine regions of the upper troposphere that are supersaturated: where the relative humidity (RH) is greater than 100%. AIRS data compare well to other in situ and satellite observations of RH and provide daily global coverage up to 200 hPa, though satellite observations of supersaturation are highly uncertain. The climatology of supersaturation is analyzed statistically to understand where supersaturation occurs and how frequently. Supersaturation occurs in humid regions of the upper tropical tropopause near convection 10%–20% of the time at 200 hPa. Supersaturation is very frequent in the extratropical upper troposphere, occurring 20%–40% of the time, and over 50% of the time in storm track regions below the tropopause. The annual cycle of supersaturation is consistent for the ∼2.5 yr of data analyzed. More supersaturation is seen in the Southern Hemisphere midlatitudes, which may be attributed to higher temperature variance.

Multimodel Analysis of the Water Vapor Feedback in the Tropical Upper Troposphere

2006 ◽  
Vol 19 (20) ◽  
pp. 5455-5464 ◽  
Author(s):  
Ken Minschwaner ◽  
Andrew E. Dessler ◽  
Parnchai Sawaengphokhai
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Sea Surface ◽  
Specific Humidity ◽  
Upper Troposphere ◽  
The Mean ◽  
Tropical Upper Troposphere

Abstract Relationships between the mean humidity in the tropical upper troposphere and tropical sea surface temperatures in 17 coupled ocean–atmosphere global climate models were investigated. This analysis builds on a prior study of humidity and surface temperature measurements that suggested an overall positive climate feedback by water vapor in the tropical upper troposphere whereby the mean specific humidity increases with warmer sea surface temperature (SST). The model results for present-day simulations show a large range in mean humidity, mean air temperature, and mean SST, but they consistently show increases in upper-tropospheric specific humidity with warmer SST. The model average increase in water vapor at 250 mb with convective mean SST is 44 ppmv K−1, with a standard deviation of 14 ppmv K−1. Furthermore, the implied feedback in the models is not as strong as would be the case if relative humidity remained constant in the upper troposphere. The model mean decrease in relative humidity is −2.3% ± 1.0% K−1 at 250 mb, whereas observations indicate decreases of −4.8% ± 1.7% K−1 near 215 mb. These two values agree within the respective ranges of uncertainty, indicating that current global climate models are simulating the observed behavior of water vapor in the tropical upper troposphere with reasonable accuracy.

scholarly journals An Evaluation of Satellite Remote Sensing Data Products for Land Surface Hydrology: Atmospheric Infrared Sounder*

2010 ◽  
Vol 11 (6) ◽  
pp. 1234-1262 ◽  
Author(s):  
Craig R. Ferguson ◽  
Eric F. Wood
Keyword(s):  
Remote Sensing ◽  
Land Surface ◽  
Remote Sensing Data ◽  
Specific Humidity ◽  
Retrieval Algorithm ◽  
Climatic Data ◽  
Atmospheric Infrared Sounder ◽  
Retrieval Models ◽  
Near Surface

Abstract The skill of instantaneous Atmospheric Infrared Sounder (AIRS) retrieved near-surface meteorology, including surface skin temperature (Ts), air temperature (Ta), specific humidity (q), and relative humidity (RH), as well as model-derived surface pressure (Psurf) and 10-m wind speed (w), is evaluated using collocated National Climatic Data Center (NCDC) in situ observations, offline data from the North American Land Data Assimilation System (NLDAS), and geostationary remote sensing (RS) data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI). Such data are needed for RS-based water cycle monitoring in areas without readily available in situ data. The study is conducted over the continental United States and Africa for a period of more than 6 years (2002–08). For both regions, it provides for the first time the geographic distribution of AIRS retrieval performance. Through conditional sampling, attribution of retrieval errors to scene atmospheric and surface conditions is performed. The findings support previous assertions that performance degrades with cloud fraction and that (positive) bias enhances with altitude. In general AIRS is biased warm and dry. In certain regions, strong AIRS–NCDC correlation suggests that bias-driven errors, which can be substantial, are correctable. The utility of the error characteristics for prescribing the input-induced uncertainty of RS retrieval models is demonstrated through two applications: a microwave soil moisture retrieval algorithm and the Penman–Monteith evapotranspiration model. An important side benefit of this study is the verification of NLDAS forcing.

Hydrologic Model Sensitivity to Temporal Aggregation of Meteorological Forcing Data: a Case Study for the Contiguous USA

2021 ◽  
Author(s):  
Ashley E. Van Beusekom ◽  
Lauren E. Hay ◽  
Andrew R. Bennett ◽  
Young-Don Choi ◽  
Martyn P. Clark ◽  
...  
Keyword(s):  
Longwave Radiation ◽  
Latin Hypercube Sampling ◽  
Temporal Variations ◽  
Hydrologic Model ◽  
Specific Humidity ◽  
Shortwave Radiation ◽  
Model Parameters ◽  
Model Output ◽  
Regional Variability ◽  
Model Sensitivity

Abstract Surface meteorological analyses are an essential input (termed ‘forcing’) for hydrologic modeling. This study investigated the sensitivity of different hydrologic model configurations to temporal variations of seven forcing variables (precipitation rate, air temperature, longwave radiation, specific humidity, shortwave radiation, wind speed, and air pressure). Specifically, the effects of temporally aggregating hourly forcings to hourly daily-average forcings were examined. The analysis was based on 14 hydrological outputs from the Structure for Unifying Multiple Modeling Alternatives (SUMMA) model for the 671 Catchment Attributes and MEteorology for Large-sample Studies (CAMELS) basins across the contiguous United States (CONUS). Results demonstrated that the hydrologic model sensitivity to temporally aggregating the forcing inputs varies across model output variables and model locations. We used Latin Hypercube sampling to sample model parameters from eight combinations of three influential model physics choices (three model decisions with two options for each decision, i.e., eight model configurations). Results showed that the choice of model physics can change the relative influence of forcing on model outputs and the forcing importance may not be dependent on the parameter space. This allows for model output sensitivity to forcing aggregation to be tested prior to parameter calibration. More generally, this work provides a comprehensive analysis of the dependence of modeled outcomes on input forcing behavior, providing insight into the regional variability of forcing variable dominance on modeled outputs across CONUS.

scholarly journals Hot extremes have become drier in the US Southwest

2020 ◽  
Author(s):  
Karen McKinnon ◽  
Andrew Poppick ◽  
Isla Simpson
Keyword(s):  
Soil Moisture ◽  
Climate Models ◽  
Summer Precipitation ◽  
American Southwest ◽  
Specific Humidity ◽  
The Past ◽  
The Us ◽  
Low Humidity ◽  
Heat Extremes

Abstract The impacts of summer heat extremes are mediated by the moisture content of the atmosphere. Increases in temperatures due to human-caused climate change are generally expected to increase specific humidity; however, it remains unclear how humidity extremes may change, especially in climatologically dry regions. Here, using in situ measurements and reanalyses, we show that specific humidity on low humidity days in the American Southwest has decreased over the past seven decades, and that the greatest decreases co-occur with the hottest temperatures. Hot, dry summers have anomalously low evapotranspiration that is linked to low summer soil moisture. The recent decrease in summer soil moisture is explained by declines in pre-summer soil moisture, whereas the interannual variability is controlled by summer precipitation. Climate models project continued declines in pre-summer soil moisture but increases in summer precipitation, leading to uncertainty as to how summer soil moisture and hot, dry days will change in the future.

scholarly journals An Analysis of Tropospheric Humidity Trends from Radiosondes

2009 ◽  
Vol 22 (22) ◽  
pp. 5820-5838 ◽  
Author(s):  
Mark P. McCarthy ◽  
P. W. Thorne ◽  
H. A. Titchner
Keyword(s):  
Relative Humidity ◽  
Climate Model ◽  
Sampling Bias ◽  
Specific Humidity ◽  
Water Vapor Feedback ◽  
Break Points ◽  
Long Term Trends ◽  
The Impact

Abstract A new analysis of historical radiosonde humidity observations is described. An assessment of both known and unknown instrument and observing practice changes has been conducted to assess their impact on bias and uncertainty in long-term trends. The processing of the data includes interpolation of data to address known sampling bias from missing dry day and cold temperature events, a first-guess adjustment for known radiosonde model changes, and a more sophisticated ensemble of estimates based on 100 neighbor-based homogenizations. At each stage the impact and uncertainty of the process has been quantified. The adjustments remove an apparent drying over Europe and parts of Asia and introduce greater consistency between temperature and specific humidity trends from day and night observations. Interannual variability and trends at the surface are shown to be in good agreement with independent in situ datasets, although some steplike discrepancies are apparent between the time series of relative humidity at the surface. Adjusted trends, accounting for documented and undocumented break points and their uncertainty, across the extratropical Northern Hemisphere lower and midtroposphere show warming of 0.1–0.4 K decade−1 and moistening on the order of 1%–5% decade−1 since 1970. There is little or no change in the observed relative humidity in the same period, consistent with climate model expectation of a positive water vapor feedback in the extratropics with near-constant relative humidity.

On the Performance of Airborne Meteorological Observations Against Other In-situ Measurements

2021 ◽  
Author(s):  
Timothy J. Wagner ◽  
Ralph A. Petersen
Keyword(s):  
Relative Humidity ◽  
Meteorological Data ◽  
Specific Humidity ◽  
Commercial Aircraft ◽  
Vapor Sensing ◽  
Moisture Performance ◽  
In Situ Observations ◽  
Meteorological Observations ◽  
One Year

AbstractRoutine in situ observations of the atmosphere taken in flight by commercial aircraft provide atmospheric profiles with greater temporal density and, in many parts of the country, at more locations than the operational radiosonde network. Thousands of daily temperature and wind observations are provided by largely complementary systems, the Airborne Meteorological Data Relay (AMDAR) and the Tropospheric Airborne Meteorological Data Reporting (TAMDAR). All TAMDAR aircraft also measure relative humidity while a subset of AMDAR aircraft are equipped with the Water Vapor Sensing System (WVSS) measure specific humidity.One year of AMDAR/WVSS and TAMDAR observations are evaluated against operational National Weather Service (NWS) radiosondes to characterize the performance of these systems in similar environments. For all observed variables, AMDAR reports showed both smaller average differences and less random differences with respect to radiosondes than the corresponding TAMDAR observations. Observed differences were not necessarily consistent with known radiosonde biases. Since the systems measure different humidity variables, moisture is evaluated in both specific and relative humidity using both aircraft and radiosonde temperatures to derive corresponding moisture variables. Derived moisture performance is improved when aircraft-based temperatures are corrected prior to conversion. AMDAR observations also show greater consistency between different aircraft than TAMDAR observations do. The small variability in coincident WVSS humidity observations indicates that they may prove more reliable than humidity observations from NWS radiosondes.

Amplified warming of extreme temperatures over tropical land

2021 ◽  
Author(s):  
Michael Byrne
Keyword(s):  
Climate Change ◽  
Relative Humidity ◽  
Land Surface ◽  
Climate Models ◽  
Future Climate ◽  
Future Climate Change ◽  
Extreme Temperatures ◽  
Near Surface ◽  
Key Factor ◽  
Change Response

<p>Extreme temperatures have warmed substantially over recent decades and are projected to continue warming in response to future climate change. Warming of extreme temperatures is amplified over land where the impacts on human health, wildfire risk and food production are most severe. Using simulations with climate models, I show that hot days over tropical land warm substantially more than the average day. For example, warming of the hottest 1% of land days is 24% larger than the time-mean warming averaged across models. The climate-change response of extreme temperatures over tropical land is interpreted using a theory based on atmospheric dynamics. According to the theory, warming is amplified for hot land days because those days are dry: I term this the "drier get hotter" mechanism. Changes in near-surface relative humidity further increase tropical land warming , with decreases in land relative humidity particularly important. The theory advances physical understanding of the tropical climate and highlights land-surface dryness as a key factor determining how extreme temperatures will respond to future climate change.</p>

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