Weak Land–Atmosphere Coupling Strength in HadAM3: The Role of Soil Moisture VariabilitySource: Journal of Hydrometeorology:;2005:;Volume( 006 ):;issue: 005::page 670DOI: 10.1175/JHM445.1Publisher: American Meteorological Society
Abstract: A recent model intercomparison, the Global Land?Atmosphere Coupling Experiment (GLACE), showed that there is a wide range of land?atmosphere coupling strengths, or the degree that soil moisture affects the generation of precipitation, amongst current atmospheric general circulation models (AGCMs). Coupling strength in the Hadley Centre atmosphere model (HadAM3) is among the weakest of all AGCMs considered in GLACE. Reasons for the weak HadAM3 coupling strength are sought here. In particular, the impact of pervasive saturated soil conditions and low soil moisture variability on coupling strength is assessed. It is found that when the soil model is modified to reduce the occurrence of soil moisture saturation and to encourage soil moisture variability, the soil moisture?precipitation feedback remains weak, even though the relationship between soil moisture and evaporation is strengthened. Composites of the diurnal cycle, constructed relative to soil moisture, indicate that the model can simulate key differences in boundary layer development over wet versus dry soils. In particular, the influence of wet or dry soil on the diurnal cycles of Bowen ratio, boundary layer height, and total heat flux are largely consistent with the observed influence of soil moisture on these properties. However, despite what appears to be successful simulation of these key aspects of the indirect soil moisture?precipitation feedback, the model does not capture observed differences for wet and dry soils in the daily accumulation of boundary layer moist static energy, a crucial feature of the feedback mechanism.
|
Collections
Show full item record
contributor author | Lawrence, David M. | |
contributor author | Slingo, Julia M. | |
date accessioned | 2017-06-09T17:13:48Z | |
date available | 2017-06-09T17:13:48Z | |
date copyright | 2005/10/01 | |
date issued | 2005 | |
identifier issn | 1525-755X | |
identifier other | ams-81452.pdf | |
identifier uri | http://onlinelibrary.yabesh.ir/handle/yetl/4224457 | |
description abstract | A recent model intercomparison, the Global Land?Atmosphere Coupling Experiment (GLACE), showed that there is a wide range of land?atmosphere coupling strengths, or the degree that soil moisture affects the generation of precipitation, amongst current atmospheric general circulation models (AGCMs). Coupling strength in the Hadley Centre atmosphere model (HadAM3) is among the weakest of all AGCMs considered in GLACE. Reasons for the weak HadAM3 coupling strength are sought here. In particular, the impact of pervasive saturated soil conditions and low soil moisture variability on coupling strength is assessed. It is found that when the soil model is modified to reduce the occurrence of soil moisture saturation and to encourage soil moisture variability, the soil moisture?precipitation feedback remains weak, even though the relationship between soil moisture and evaporation is strengthened. Composites of the diurnal cycle, constructed relative to soil moisture, indicate that the model can simulate key differences in boundary layer development over wet versus dry soils. In particular, the influence of wet or dry soil on the diurnal cycles of Bowen ratio, boundary layer height, and total heat flux are largely consistent with the observed influence of soil moisture on these properties. However, despite what appears to be successful simulation of these key aspects of the indirect soil moisture?precipitation feedback, the model does not capture observed differences for wet and dry soils in the daily accumulation of boundary layer moist static energy, a crucial feature of the feedback mechanism. | |
publisher | American Meteorological Society | |
title | Weak Land–Atmosphere Coupling Strength in HadAM3: The Role of Soil Moisture Variability | |
type | Journal Paper | |
journal volume | 6 | |
journal issue | 5 | |
journal title | Journal of Hydrometeorology | |
identifier doi | 10.1175/JHM445.1 | |
journal fristpage | 670 | |
journal lastpage | 680 | |
tree | Journal of Hydrometeorology:;2005:;Volume( 006 ):;issue: 005 | |
contenttype | Fulltext |