Abstract. A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aeros... more Abstract. A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aerosol-Cloud inter-action scheme (McRAS-AC) including, among others, a new ice nucleation parameterization, is implemented in the GEOS-5 AGCM. Various fields from a 10-yr-long integra-tion of the AGCM with McRAS-AC are compared with their counterparts from an integration of the baseline GEOS-5 AGCM, as well as satellite observations. Generally McRAS-AC simulations have smaller biases in cloud fields and cloud radiative effects over most of the regions of the Earth than the baseline GEOS-5 AGCM. Two systematic biases are identi-fied in the McRAS-AC runs: one is underestimation of cloud particle numbers around 40 ◦ S–60 ◦ S, and one is overesti-mate of cloud water path during the Northern Hemisphere summer over the Gulf Stream and North Pacific. Sensitivity
Aspects of the angular momentum cycle, energetics, and related diagnostics from a number of model... more Aspects of the angular momentum cycle, energetics, and related diagnostics from a number of models, including some from the Goddard Laboratory for Atmospheres, and from the Atmospheric Model Intercomparison Project (AMIP) are examined. Torques that dynamically excite changes in angular momentum, including strong torques at mountains were studied. The measure of how atmospheric mass from a strong weather signal can notably change the angular momentum is studied. For AMIP, there is a spread in the angular momentum amongst models, while the GLA model does reasonably well compared to the other models in the diagnostics examined, namely angular momentum and water vapor. Trends and interannual variability in water vapor over a lengthy period was examined. The role of the diabatic heating components, especially latent heating, in the energy cycle and the terms converting available potential energy to kinetic energy, among other parts of the energy cycle, are studied. Modes of climate of th...
Extreme seasonal fluctuations of the surface-air temperature characterize the climate of central ... more Extreme seasonal fluctuations of the surface-air temperature characterize the climate of central Europe, 45-60 deg North Temperature difference between warm 1990 and cold 1996 in the January-March period, persisting for more than two weeks at a time, amounted to 18 C for extensive areas. These anomalies in the surface-air temperature stem in the first place from differences in the low level flow from the eastern North-Atlantic: the value of the Index 1na of southwesterlies over the eastern North-Atlantic was 8.0 m/s in February 1990, but only 2.6 m/ s in February 1996. The primary forcing by warm advection to positive anomalies in monthly mean surface temperature produced strong synoptic-scale uplift at the 700 mb level over some regions in Europe. The strong uplift contributed in 1990 to a much larger cloud-cover over central Europe, which reduced heat-loss to space (greenhouse effect). Thus, spring arrived earlier than usual in 1990, but later than usual in 1996.
A simple but realistic biosphere model for calculating the transfer of energy, mass and momentum ... more A simple but realistic biosphere model for calculating the transfer of energy, mass and momentum between the atmosphere and the vegetated surface of the Earth has been developed for use in atmospheric general circulation models.
A simple water budget model is used to get a characteristic time scale of the soil hydrology, whi... more A simple water budget model is used to get a characteristic time scale of the soil hydrology, which is defined as the time scale for the onset of agricultural droughts. Assuming that there is no rain, our estimation requires as input the knowledge of the initial soil moisture content and an evaluation of the potential evaporation. Two applications at a global scale are shown. In a first case an initially saturated soil is considered to get an estimation of the time needed by a climate model to adjust realistically to initial errors in the soil moisture distribution. In a second case climatological values are used as initial conditions to get a measure of the sensitivity of the hydrological cycle to the atmospheric forcing.
Public reporting burden for thiscollection of information is estimated to average 1 hour per resp... more Public reporting burden for thiscollection of information is estimated to average 1 hour per response, includingthe time for reviewinginstructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimale or any other aspect of this collection of information, includingsuggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports,
Forty years of precipitation and surface temperature data observed over 261 Local Climatic Data (... more Forty years of precipitation and surface temperature data observed over 261 Local Climatic Data (LCD) stations in the Continental United States was utilized in a ground hydrology model to yield soil moisture time series at each station. A month-by-month soil moisture dataset was constructed for each year. The monthly precipitation was correlated with antecedent monthly precipitation, soil moisture and vapotranspiration separately. The maximum positive correlation is found to be in the drought prone western Great Plains region during the latter part of summer. There is also some negative correlation in coastal regions. The correlations between soil moisture and precipitation particularly in the latter part of summer, suggest that large scale droughts over extended periods may be partially maintained by the feedback influence of soil moisture on rainfall. In many other regions the lack of positive correlation shows that there is no simple answer such as higher land-surface evapotransp...
Real clouds and clouds systems are inherently three dimensional (3D). Because of the limitations ... more Real clouds and clouds systems are inherently three dimensional (3D). Because of the limitations in computer resources, however, most cloud-resolving models (CRMs) today are still two-dimensional (2D). A few 3D CRMs have been used to study the response of clouds to large-scale forcing. In these 3D simulations, the model domain was small, and the integration time was 6 hours. Only recently have 3D experiments been performed for multi-day periods for tropical cloud system with large horizontal domains at the National Center for Atmospheric Research. The results indicate that surface precipitation and latent heating profiles are very similar between the 2D and 3D simulations of these same cases. The reason for the strong similarity between the 2D and 3D CRM simulations is that the observed large-scale advective tendencies of potential temperature, water vapor mixing ratio, and horizontal momentum were used as the main forcing in both the 2D and 3D models. Interestingly, the 2D and 3D v...
Precipitation recycling is defined as the amount of water that evaporates from a region that prec... more Precipitation recycling is defined as the amount of water that evaporates from a region that precipitates within the same region. This is also interpreted as the local source of water for precipitation. In this study, the local and remote sources of water for precipitation have been diagnosed through the use of passive constituent tracers that represent regional evaporative sources along
Abstract. A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aeros... more Abstract. A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aerosol-Cloud inter-action scheme (McRAS-AC) including, among others, a new ice nucleation parameterization, is implemented in the GEOS-5 AGCM. Various fields from a 10-yr-long integra-tion of the AGCM with McRAS-AC are compared with their counterparts from an integration of the baseline GEOS-5 AGCM, as well as satellite observations. Generally McRAS-AC simulations have smaller biases in cloud fields and cloud radiative effects over most of the regions of the Earth than the baseline GEOS-5 AGCM. Two systematic biases are identi-fied in the McRAS-AC runs: one is underestimation of cloud particle numbers around 40 ◦ S–60 ◦ S, and one is overesti-mate of cloud water path during the Northern Hemisphere summer over the Gulf Stream and North Pacific. Sensitivity
Aspects of the angular momentum cycle, energetics, and related diagnostics from a number of model... more Aspects of the angular momentum cycle, energetics, and related diagnostics from a number of models, including some from the Goddard Laboratory for Atmospheres, and from the Atmospheric Model Intercomparison Project (AMIP) are examined. Torques that dynamically excite changes in angular momentum, including strong torques at mountains were studied. The measure of how atmospheric mass from a strong weather signal can notably change the angular momentum is studied. For AMIP, there is a spread in the angular momentum amongst models, while the GLA model does reasonably well compared to the other models in the diagnostics examined, namely angular momentum and water vapor. Trends and interannual variability in water vapor over a lengthy period was examined. The role of the diabatic heating components, especially latent heating, in the energy cycle and the terms converting available potential energy to kinetic energy, among other parts of the energy cycle, are studied. Modes of climate of th...
Extreme seasonal fluctuations of the surface-air temperature characterize the climate of central ... more Extreme seasonal fluctuations of the surface-air temperature characterize the climate of central Europe, 45-60 deg North Temperature difference between warm 1990 and cold 1996 in the January-March period, persisting for more than two weeks at a time, amounted to 18 C for extensive areas. These anomalies in the surface-air temperature stem in the first place from differences in the low level flow from the eastern North-Atlantic: the value of the Index 1na of southwesterlies over the eastern North-Atlantic was 8.0 m/s in February 1990, but only 2.6 m/ s in February 1996. The primary forcing by warm advection to positive anomalies in monthly mean surface temperature produced strong synoptic-scale uplift at the 700 mb level over some regions in Europe. The strong uplift contributed in 1990 to a much larger cloud-cover over central Europe, which reduced heat-loss to space (greenhouse effect). Thus, spring arrived earlier than usual in 1990, but later than usual in 1996.
A simple but realistic biosphere model for calculating the transfer of energy, mass and momentum ... more A simple but realistic biosphere model for calculating the transfer of energy, mass and momentum between the atmosphere and the vegetated surface of the Earth has been developed for use in atmospheric general circulation models.
A simple water budget model is used to get a characteristic time scale of the soil hydrology, whi... more A simple water budget model is used to get a characteristic time scale of the soil hydrology, which is defined as the time scale for the onset of agricultural droughts. Assuming that there is no rain, our estimation requires as input the knowledge of the initial soil moisture content and an evaluation of the potential evaporation. Two applications at a global scale are shown. In a first case an initially saturated soil is considered to get an estimation of the time needed by a climate model to adjust realistically to initial errors in the soil moisture distribution. In a second case climatological values are used as initial conditions to get a measure of the sensitivity of the hydrological cycle to the atmospheric forcing.
Public reporting burden for thiscollection of information is estimated to average 1 hour per resp... more Public reporting burden for thiscollection of information is estimated to average 1 hour per response, includingthe time for reviewinginstructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimale or any other aspect of this collection of information, includingsuggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports,
Forty years of precipitation and surface temperature data observed over 261 Local Climatic Data (... more Forty years of precipitation and surface temperature data observed over 261 Local Climatic Data (LCD) stations in the Continental United States was utilized in a ground hydrology model to yield soil moisture time series at each station. A month-by-month soil moisture dataset was constructed for each year. The monthly precipitation was correlated with antecedent monthly precipitation, soil moisture and vapotranspiration separately. The maximum positive correlation is found to be in the drought prone western Great Plains region during the latter part of summer. There is also some negative correlation in coastal regions. The correlations between soil moisture and precipitation particularly in the latter part of summer, suggest that large scale droughts over extended periods may be partially maintained by the feedback influence of soil moisture on rainfall. In many other regions the lack of positive correlation shows that there is no simple answer such as higher land-surface evapotransp...
Real clouds and clouds systems are inherently three dimensional (3D). Because of the limitations ... more Real clouds and clouds systems are inherently three dimensional (3D). Because of the limitations in computer resources, however, most cloud-resolving models (CRMs) today are still two-dimensional (2D). A few 3D CRMs have been used to study the response of clouds to large-scale forcing. In these 3D simulations, the model domain was small, and the integration time was 6 hours. Only recently have 3D experiments been performed for multi-day periods for tropical cloud system with large horizontal domains at the National Center for Atmospheric Research. The results indicate that surface precipitation and latent heating profiles are very similar between the 2D and 3D simulations of these same cases. The reason for the strong similarity between the 2D and 3D CRM simulations is that the observed large-scale advective tendencies of potential temperature, water vapor mixing ratio, and horizontal momentum were used as the main forcing in both the 2D and 3D models. Interestingly, the 2D and 3D v...
Precipitation recycling is defined as the amount of water that evaporates from a region that prec... more Precipitation recycling is defined as the amount of water that evaporates from a region that precipitates within the same region. This is also interpreted as the local source of water for precipitation. In this study, the local and remote sources of water for precipitation have been diagnosed through the use of passive constituent tracers that represent regional evaporative sources along
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