scholarly journals Role of surface hydrology in determining the seasonal cycle of Indian summer monsoon in a general circulation model

2016 ◽  
Author(s):  
Shubhi Agrawal ◽  
Arindam Chakraborty
Keyword(s):  
Soil Moisture ◽  
Summer Monsoon ◽  
Early Onset ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Moisture Convergence ◽  
Surface Hydrology ◽  
Gangetic Plain ◽  
Near Surface ◽  
Local Soil

Abstract. Rainfall during summer monsoon season (June–September; JJAS), that accounts for about 80 % of the yearly total over Indian region, is herald by its onset over Kerala in June. And these four summer monsoon months contribute 19 %, 32 %, 29 % and 20 % of the seasonal rainfall, respectively. Therefore, it is important that this seasonal cycle is captured by general circulation models (GCMs) used to understand and predict monsoon. In this study, using decade-long simulations of an atmospheric GCM, we show that surface hydrology over India as well as over its surrounding regions plays a central role during the onset phase of monsoon and thus modulates seasonal cycle. The model, in its default configuration, simulates early onset and excess precipitation (about double of that observed) over the Gangetic plain (GP) in June. Moreover, the model has large positive surface soil moisture bias over India throughout the year and negative bias over the arid-semiarid regions to the north-west of India during the pre-monsoon months. From multiple sensitivity experiments, it is discerned that the remote dry soil moisture bias in the model over the Western Central Asia region intensifies the tropospheric low-level circulation causing excessive moisture advection, followed by moisture convergence over the GP in the beginning of June, and an early onset. Local soil moisture over GP makes a diminutive contribution to precipitation bias in June. But as the season progresses and the remote influence weakens, the increased local soil moisture regulates surface and near-surface conditions which subsequently reduces moisture convergence over GP, reducing precipitation in the later phase of monsoon. The results presented here can be useful for diagnosis and improvement of land surface models.

scholarly journals Impacts of Local Soil Moisture Anomalies on the Atmospheric Circulation and on Remote Surface Meteorological Fields during Boreal Summer: A Comprehensive Analysis over North America

2016 ◽  
Vol 29 (20) ◽  
pp. 7345-7364 ◽  
Author(s):  
Randal D. Koster ◽  
Yehui Chang ◽  
Hailan Wang ◽  
Siegfried D. Schubert
Keyword(s):  
Soil Moisture ◽  
North America ◽  
Atmospheric Circulation ◽  
General Circulation ◽  
Boreal Summer ◽  
Near Surface ◽  
Local Soil ◽  
Lower Mississippi River ◽  
Continental Interior ◽  
The U.S

Abstract A series of stationary wave model (SWM) experiments are performed in which the boreal summer atmosphere is forced, over a number of locations in the continental United States, with an idealized diabatic heating anomaly that mimics the atmospheric heating associated with a dry land surface. For localized heating within a large portion of the continental interior, regardless of the specific location of this heating, the spatial pattern of the forced atmospheric circulation anomaly (in terms of 250-hPa eddy streamfunction) is largely the same: a high anomaly forms over west-central North America and a low anomaly forms to the east. In supplemental atmospheric general circulation model (AGCM) experiments, similar results are found; imposing soil moisture dryness in the AGCM in different locations within the U.S. interior tends to produce the aforementioned pattern, along with an associated near-surface warming and precipitation deficit in the center of the continent. The SWM-based and AGCM-based patterns generally agree with composites generated using reanalysis and precipitation gauge data. The AGCM experiments also suggest that dry anomalies imposed in the lower Mississippi River valley have remote surface impacts of particularly large spatial extent, and a region along the eastern half of the U.S.–Canadian border is particularly sensitive to dry anomalies in a number of remote areas. Overall, the SWM and AGCM experiments support the idea of a positive feedback loop operating over the continent: dry surface conditions in many interior locations lead to changes in atmospheric circulation that act to enhance further the overall dryness of the continental interior.

HAPEX—MOBILHY: A Hydrologic Atmospheric Experiment the Study of Water Budget and Evaporation Flux at the Climatic Scale

1986 ◽  
Vol 67 (2) ◽  
pp. 138-144 ◽  
Author(s):  
Jean-Claude André ◽  
Jean-Paul Goutorbe ◽  
Alain Perrier
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Land Surface ◽  
Water Budget ◽  
General Circulation ◽  
Circulation Model ◽  
Surface Energy Budget ◽  
Surface Hydrology ◽  
Land Surface Water ◽  
Evaporation Flux

The HAPEX-MOBILHY program is aimed at studying the hydrological budget and evaporation flux at the scale of a GCM (general circulation model) grid square, i.e., 104 km2. Different surface and subsurface networks will be operated during the year 1986, to measure and monitor soil moisture, surface-energy budget and surface hydrology, as well as atmospheric properties. A two-and-a-half-month special observing period will allow for detailed measurements of atmospheric fluxes and for intensive remote sensing of surface properties using well-instrumented aircraft. The main objective of the program, for which guest investigations are strongly encouraged, is to provide a data base against which parameterization schemes for the land-surface water budget will be tested and developed.

scholarly journals Investigating soil moisture-climate interactions with prescribed soil moisture experiments: an assessment with the Community Earth System Model (version 1.2)

2016 ◽  
Author(s):  
Mathias Hauser ◽  
René Orth ◽  
Sonia I. Seneviratne
Keyword(s):  
Soil Moisture ◽  
Water Balance ◽  
Land Surface ◽  
Seasonal Cycle ◽  
Deep Soil ◽  
Surface Hydrology ◽  
Climate Interactions ◽  
Set Up ◽  
Moisture Conditions ◽  
The Impact

Abstract. Land surface hydrology is an important control of surface weather and climate. A valuable technique to investigate this link is the prescription of soil moisture in land surface models, which leads to a decoupling of the interaction between the atmosphere and land processes. Diverse approaches to prescribe soil moisture, as well as different prescribed soil moisture conditions can be envisaged. Here, we compare and assess three methodologies to prescribe soil moisture and investigate the impact of two estimates of the climatological seasonal cycle to prescribe soil moisture. This can help to guide the set up of future experiments prescribing soil moisture, as for instance planned within the "Land Surface, Snow and Soil Moisture Model Intercomparison Project" (LS3MIP). Our analysis shows that, though in appearance similar, the different approaches require substantially different long-term moisture inputs and lead to different temperature signals. The smallest influence on temperature and the water balance is found when prescribing the median seasonal cycle of deep soil liquid water, whereas the strongest signal is found when prescribing soil liquid and soil ice using the mean seasonal cycle. These results indicate that induced net water-balance perturbations in experiments investigating soil moisture-climate coupling are important contributors to the climate response, in addition to the intended impact of the decoupling.

scholarly journals Realistic Initialization of Land Surface States: Impacts on Subseasonal Forecast Skill

2004 ◽  
Vol 5 (6) ◽  
pp. 1049-1063 ◽  
Author(s):  
Randal D. Koster ◽  
Max J. Suarez ◽  
Ping Liu ◽  
Urszula Jambor ◽  
Aaron Berg ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Air Temperature ◽  
Land Surface ◽  
General Circulation ◽  
Surface States ◽  
Forecast Skill ◽  
Precipitation Forecast ◽  
Surface Model ◽  
Monthly Precipitation ◽  
Near Surface

Abstract Forcing a land surface model (LSM) offline with realistic global fields of precipitation, radiation, and near-surface meteorology produces realistic fields (within the context of the LSM) of soil moisture, temperature, and other land surface states. These fields can be used as initial conditions for precipitation and temperature forecasts with an atmospheric general circulation model (AGCM). Their usefulness is tested in this regard by performing retrospective 1-month forecasts (for May through September, 1979–93) with the NASA Global Modeling and Assimilation Office (GMAO) seasonal prediction system. The 75 separate forecasts provide an adequate statistical basis for quantifying improvements in forecast skill associated with land initialization. Evaluation of skill is focused on the Great Plains of North America, a region with both a reliable land initialization and an ability of soil moisture conditions to overwhelm atmospheric chaos in the evolution of the meteorological fields. The land initialization does cause a small but statistically significant improvement in precipitation and air temperature forecasts in this region. For precipitation, the increases in forecast skill appear strongest in May through July, whereas for air temperature, they are largest in August and September. The joint initialization of land and atmospheric variables is considered in a supplemental series of ensemble monthly forecasts. Potential predictability from atmospheric initialization dominates over that from land initialization during the first 2 weeks of the forecast, whereas during the final 2 weeks, the relative contributions from the two sources are of the same order. Both land and atmospheric initialization contribute independently to the actual skill of the monthly temperature forecast, with the greatest skill derived from the initialization of both. Land initialization appears to contribute the most to monthly precipitation forecast skill.

scholarly journals Investigating soil moisture–climate interactions with prescribed soil moisture experiments: an assessment with the Community Earth System Model (version 1.2)

2017 ◽  
Vol 10 (4) ◽  
pp. 1665-1677 ◽  
Author(s):  
Mathias Hauser ◽  
René Orth ◽  
Sonia I. Seneviratne
Keyword(s):  
Soil Moisture ◽  
Water Balance ◽  
Land Surface ◽  
Seasonal Cycle ◽  
Deep Soil ◽  
Surface Hydrology ◽  
Climate Interactions ◽  
Set Up ◽  
Moisture Conditions ◽  
The Impact

Abstract. Land surface hydrology is an important control of surface weather and climate. A valuable technique to investigate this link is the prescription of soil moisture in land surface models, which leads to a decoupling of the atmosphere and land processes. Diverse approaches to prescribe soil moisture, as well as different prescribed soil moisture conditions have been used in previous studies. Here, we compare and assess four methodologies to prescribe soil moisture and investigate the impact of two different estimates of the climatological seasonal cycle used to prescribe soil moisture. Our analysis shows that, though in appearance similar, the different approaches require substantially different long-term moisture inputs and lead to different temperature signals. The smallest influence on temperature and the water balance is found when prescribing the median seasonal cycle of deep soil liquid water, whereas the strongest signal is found when prescribing soil liquid and soil ice using the mean seasonal cycle. These results indicate that induced net water-balance perturbations in experiments investigating soil moisture–climate coupling are important contributors to the climate response, in addition to the intended impact of the decoupling. These results help to guide the set-up of future experiments prescribing soil moisture, as for instance planned within the Land Surface, Snow and Soil Moisture Model Intercomparison Project (LS3MIP).

scholarly journals Causal Pathways for Temperature Predictability from Snow Depth

2017 ◽  
Vol 30 (23) ◽  
pp. 9651-9663 ◽  
Author(s):  
Erik W. Kolstad
Keyword(s):  
Soil Moisture ◽  
Snow Depth ◽  
Seasonal Cycle ◽  
Weather Forecasting ◽  
Surface Air Temperature ◽  
Early Summer ◽  
Near Surface ◽  
Temperature Anomalies ◽  
Causal Pathways ◽  
Melting Season

Dynamical subseasonal-to-seasonal (S2S) weather forecasting has made strides in recent years, thanks partly to better initialization and representation of physical variables in models. For instance, realistic initializations of snow and soil moisture in models yield enhanced temperature predictability on S2S time scales. Snow depth and soil moisture also mediate month-to-month persistence of near-surface air temperature. Here the role of snow depth as predictor of temperature one month ahead in the Northern Hemisphere is examined via two causal pathways. Through the first pathway, snow depth anomalies in month 1 persist into month 2 and are then linked to temperature anomalies through snow–temperature feedback mechanisms. The first pathway is active from fall to summer, and its effect peaks before the melting season: in winter in the low latitudes, in spring in the midlatitudes, and in early summer in the high latitudes. The second pathway, where snow depth anomalies in month 1 lead to soil moisture anomalies in month 2 (through melting), which are then linked to temperature anomalies in month 2 through soil moisture–temperature feedbacks, is most active in spring and summer. The effect of the second pathway peaks during the melting season, namely, later in the year than the first pathway. The latitudes of the highest mediated effect through both pathways follow a seasonal cycle, shifting northward along with the seasonal insolation cycle. In keeping with this seasonal cycle, the highest snow depth mediation occurs to the north and the highest soil moisture mediation to the south of the latitudes with the highest overall temperature predictability from snow depth.

Sensitivity of Global Tropical Climate to Land Surface Processes: Mean State and Interannual Variability

2013 ◽  
Vol 26 (5) ◽  
pp. 1818-1837 ◽  
Author(s):  
Hsi-Yen Ma ◽  
Heng Xiao ◽  
C. Roberto Mechoso ◽  
Yongkang Xue
Keyword(s):  
Soil Moisture ◽  
Indirect Effect ◽  
Land Surface ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Global Climate ◽  
Circulation Model ◽  
Equatorial Pacific ◽  
Surface Processes ◽  
Mean State

Abstract This study examines the sensitivity of the global climate to land surface processes (LSP) using an atmospheric general circulation model both uncoupled (with prescribed SSTs) and coupled to an oceanic general circulation model. The emphasis is on the interactive soil moisture and vegetation biophysical processes, which have first-order influence on the surface energy and water budgets. The sensitivity to those processes is represented by the differences between model simulations, in which two land surface schemes are considered: 1) a simple land scheme that specifies surface albedo and soil moisture availability and 2) the Simplified Simple Biosphere Model (SSiB), which allows for consideration of interactive soil moisture and vegetation biophysical process. Observational datasets are also employed to assess the extent to which results are realistic. The mean state sensitivity to different LSP is stronger in the coupled mode, especially in the tropical Pacific. Furthermore, the seasonal cycle of SSTs in the equatorial Pacific, as well as the ENSO frequency, amplitude, and locking to the seasonal cycle of SSTs, is significantly modified and more realistic with SSiB. This outstanding sensitivity of the atmosphere–ocean system develops through changes in the intensity of equatorial Pacific trades modified by convection over land. The results further demonstrate that the direct impact of land–atmosphere interactions on the tropical climate is modified by feedbacks associated with perturbed oceanic conditions (“indirect effect” of LSP). The magnitude of such an indirect effect is strong enough to suggest that comprehensive studies on the importance of LSP on the global climate have to be made in a system that allows for atmosphere–ocean interactions.

scholarly journals A Revised Hydrology for the ECMWF Model: Verification from Field Site to Terrestrial Water Storage and Impact in the Integrated Forecast System

2009 ◽  
Vol 10 (3) ◽  
pp. 623-643 ◽  
Author(s):  
Gianpaolo Balsamo ◽  
Anton Beljaars ◽  
Klaus Scipal ◽  
Pedro Viterbo ◽  
Bart van den Hurk ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Soil Texture ◽  
Land Surface ◽  
Model Verification ◽  
Field Site ◽  
Forecast System ◽  
Surface Hydrology ◽  
Near Surface ◽  
Basin Scale ◽  
Terrestrial Water

Abstract The Tiled ECMWF Scheme for Surface Exchanges over Land (TESSEL) is used operationally in the Integrated Forecast System (IFS) for describing the evolution of soil, vegetation, and snow over the continents at diverse spatial resolutions. A revised land surface hydrology (H-TESSEL) is introduced in the ECMWF operational model to address shortcomings of the land surface scheme, specifically the lack of surface runoff and the choice of a global uniform soil texture. New infiltration and runoff schemes are introduced with a dependency on the soil texture and standard deviation of orography. A set of experiments in stand-alone mode is used to assess the improved prediction of soil moisture at the local scale against field site observations. Comparison with basin-scale water balance (BSWB) and Global Runoff Data Centre (GRDC) datasets indicates a consistently larger dynamical range of land water mass over large continental areas and an improved prediction of river runoff, while the effect on atmospheric fluxes is fairly small. Finally, the ECMWF data assimilation and prediction systems are used to verify the effect on surface and near-surface quantities in the atmospheric-coupled mode. A midlatitude error reduction is seen both in soil moisture and in 2-m temperature.

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