Twice‐daily monsoon precipitation maxima in the Himalayas driven by land surface effects

AbstractThe East Asia summer monsoon transition zone, a unique area of transition from humid monsoon to arid continental climate, has the most prominent aridification in the world, and has experienced land surface aridification (LSA) in recent years. To investigate the influence of LSA on regional monsoon precipitation, two numerical experiments were run for vegetation degradation over a long period (30 years). Then, precipitation variation of different magnitudes was analyzed. After that, the mechanism of LSA influence on precipitation was studied. The results show that aridification reduced average summer precipitation by 5%. Additionally, LSA considerably changed the frequency of precipitation. Unlike aridification in North Africa caused by albedo variation, LSA in our study area mainly reduced surface thermal capacity, increased surface temperature, sharply increased the transport of surface sensible heat, and raised the atmospheric convective boundary layer. This reduces atmospheric moist static energy, which is not conducive to the generation of precipitation. LSA also increases the surface landscape gradient, local horizontal gradient of land surface turbulent flux, and probability of heavy convective precipitation. This paper reveals the mechanism by which land surface anomalies affect precipitation, which lays a foundation for follow-up studies.

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Understanding land surface response to changing South Asian monsoon in a warming climate

Earth System Dynamics ◽

10.5194/esd-6-569-2015 ◽

2015 ◽

Vol 6 (2) ◽

pp. 569-582 ◽

Cited By ~ 5

Author(s):

M. V. S Ramarao ◽

R. Krishnan ◽

J. Sanjay ◽

T. P. Sabin

Keyword(s):

Climate Change ◽

South Asian ◽

Land Surface ◽

Asian Monsoon ◽

Global Climate ◽

Monsoon Circulation ◽

South Asian Monsoon ◽

Monsoon Precipitation ◽

Surface Response ◽

Regional Land

Abstract. Recent studies have drawn attention to a significant weakening trend of the South Asian monsoon circulation and an associated decrease in regional rainfall during the last few decades. While surface temperatures over the region have steadily risen during this period, most of the CMIP (Coupled Model Intercomparison Project) global climate models have difficulties in capturing the observed decrease of monsoon precipitation, thus limiting our understanding of the regional land surface response to monsoonal changes. This problem is investigated by performing two long-term simulation experiments, with and without anthropogenic forcing, using a variable resolution global climate model having high-resolution zooming over the South Asian region. The present results indicate that anthropogenic effects have considerably influenced the recent weakening of the monsoon circulation and decline of precipitation. It is seen that the simulated increase of surface temperature over the Indian region during the post-1950s is accompanied by a significant decrease of monsoon precipitation and soil moisture. Our analysis further reveals that the land surface response to decrease of soil moisture is associated with significant reduction in evapotranspiration over the Indian land region. A future projection, based on the representative concentration pathway 4.5 (RCP4.5) scenario of the Intergovernmental Panel on Climate Change (IPCC), using the same high-resolution model indicates the possibility for detecting the summer-time soil drying signal over the Indian region during the 21st century in response to climate change. Given that these monsoon hydrological changes have profound socio-economic implications the present findings provide deeper insights and enhance our understanding of the regional land surface response to the changing South Asian monsoon. While this study is based on a single model realization, it is highly desirable to have multiple realizations to establish the robustness of the results.

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LAND SURFACE EFFECTS AND THERMAL PERFORMANCE IN HOT-HUMID CLIMATE AREA

International Journal of Geomate ◽

10.21660/2019.62.icee5 ◽

2019 ◽

Vol 17 (62) ◽

Author(s):

Mustamin Rahim

Keyword(s):

Thermal Performance ◽

Land Surface ◽

Surface Effects ◽

Humid Climate ◽

Hot Humid Climate

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Urban and land surface effects on the 30 July 2003 mesoscale convective system event observed in the southern Great Plains

Journal of Geophysical Research Atmospheres ◽

10.1029/2005jd006746 ◽

2006 ◽

Vol 111 (D19) ◽

Cited By ~ 85

Author(s):

Dev Niyogi ◽

Teddy Holt ◽

Sharon Zhong ◽

Patrick C. Pyle ◽

Jeffery Basara

Keyword(s):

Great Plains ◽

Land Surface ◽

Mesoscale Convective System ◽

Surface Effects ◽

Convective System ◽

Southern Great Plains ◽

Mesoscale Convective

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REDCAPP (v1.0): parameterizing valley inversions in air temperature data downscaled from reanalyses

Geoscientific Model Development ◽

10.5194/gmd-10-2905-2017 ◽

2017 ◽

Vol 10 (8) ◽

pp. 2905-2923 ◽

Cited By ~ 9

Author(s):

Bin Cao ◽

Stephan Gruber ◽

Tingjun Zhang

Keyword(s):

Air Temperature ◽

Land Surface ◽

Surface Air Temperature ◽

Surface Effects ◽

Model Parameters ◽

Fine Scale ◽

Mountain Areas ◽

Near Surface ◽

Cold Air ◽

The Difference

Abstract. In mountain areas, the use of coarse-grid reanalysis data for driving fine-scale models requires downscaling of near-surface (e.g., 2 m high) air temperature. Existing approaches describe lapse rates well but differ in how they include surface effects, i.e., the difference between the simulated 2 m and upper-air temperatures. We show that different treatment of surface effects result in some methods making better predictions in valleys while others are better in summit areas. We propose the downscaling method REDCAPP (REanalysis Downscaling Cold Air Pooling Parameterization) with a spatially variable magnitude of surface effects. Results are evaluated with observations (395 stations) from two mountain regions and compared with three reference methods. Our findings suggest that the difference between near-surface air temperature and pressure-level temperature (ΔT) is a good proxy of surface effects. It can be used with a spatially variable land-surface correction factor (LSCF) for improving downscaling results, especially in valleys with strong surface effects and cold air pooling during winter. While LSCF can be parameterized from a fine-scale digital elevation model (DEM), the transfer of model parameters between mountain ranges needs further investigation.

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Role of Antecedent Land Surface Conditions on North American Monsoon Rainfall Variability*

Journal of Climate ◽

10.1175/jcli3387.1 ◽

2005 ◽

Vol 18 (16) ◽

pp. 3104-3121 ◽

Cited By ~ 49

Author(s):

Chunmei Zhu ◽

Dennis P. Lettenmaier ◽

Tereza Cavazos

Keyword(s):

North American ◽

Land Surface ◽

Snow Water Equivalent ◽

Rainfall Variability ◽

Winter Precipitation ◽

Early Summer ◽

North American Monsoon ◽

Mountainous Region ◽

Monsoon Precipitation ◽

Surface Conditions

Abstract Possible links between North American Monsoon System (NAMS) seasonal [June–July–August–September (JJAS)] precipitation and premonsoon seasonal land surface conditions including precipitation (P), surface air temperature (Ts), soil moisture (Sm), and snow water equivalent (SWE) anomalies are explored during the 1950–2000 period. A statistically significant inverse relationship is found between monsoon precipitation in an area defined as the Monsoon West (Arizona and western New Mexico) and antecedent winter precipitation in the southwestern (SW) United States and the mountainous region in Utah and Colorado (the predictor area). This linkage is strong during 1965–90 and weak otherwise, as has been suggested by previous studies. A land surface feedback hypothesis is proposed to explain this relationship: more winter P leads to more winter and early spring SWE in the predictor area, hence more spring and early summer Sm, and lower spring and early summer Ts, which induces a weaker onset (and less precipitation) of the NAMS and vice versa. All three links in this hypothesis were tested and the existence of a land memory associated with winter precipitation and snow, which can persist until June, was confirmed. However, the results show that this land memory contributes little to the magnitude of NAM precipitation. Winter snow is negatively correlated to late spring Ts in the SW mountainous region, but not in extreme years. In fact, the premonsoon (June) Ts over the U.S. southwest is inversely related to monsoon precipitation, which is the reverse of what is expected based on the hypothesis. The lack of a significant Sm–Ts–P relationship in most of the SW suggests, based on the constructed Sm dataset, that local premonsoon soil wetness conditions play a minor role in the strength of the monsoon. A strong positive relationship between June Ts anomalies and the large-scale midtropospheric circulation before the onset of the monsoon was found, suggesting that the controlling factor for the premonsoon Ts anomalies may not be local (i.e., not from the land surface). The results suggest that further research is needed to elucidate the nature of land–sea–atmosphere interactions as related to the onset of the monsoon.

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