Orographic effects on precipitating clouds

Houze, Robert A.

doi:10.1029/2011rg000365

Cited by 645 publications

(565 citation statements)

References 224 publications

(336 reference statements)

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“…The convergence of low-level moist air in the valley upstream to Ukhimath Tehsil and the development of a strong north-westerly dry wind above the ridges, pushes the potentially unstable air mass eastward over the protruding foothills of the Himalayas, which generates the necessary uplift to erode the lid and trigger convection. This orographic lifting of potentially unstable air acts as a trigger mechanism for deep convection over this region, which is consistent with and corroborates the findings from previous studies (Sawyer, 1947;Houze et al, 2007;Medina et al, 2010;Houze, 2012).…”

Section: Mechanism Of Convection Initiation At Ukhimath Tehsilsupporting

confidence: 92%

Improved understanding of an extreme rainfall event at the Himalayan foothills – a case study using COSMO

Shrestha

Dimri

Schomburg

et al. 2015

Tellus A: Dynamic Meteorology and Oceanography

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A B S T R A C TIn recent years, an increased occurrence of loss and damage of property and human casualties over the southern rim area of the Himalayas, caused by landslides following intense rainfall events, has been reported. An analysis of Tropical Rainfall Measuring Mission (TRMM)-gridded rainfall data shows that events with an exceedance probability of 1.6% for 200 mm/d rainfall are common over this region during the monsoon season. An improved understanding of the mechanisms, which lead to such events, is important for their prediction and to estimate the impact of climate change on their recurrence. In this study, we analyse such an extreme precipitation event, which hit the Uttarakhand region of the central Himalayas on 13 September 2012. We use the operational regional weather forecast model COSMO at a convection-permitting resolution of 2.8 km to simulate this event. The spatial pattern of daily-accumulated precipitation and atmospheric state profiles simulated by the model compared well with the TRMM-gridded data and radiosonde observations, which adds confidence to our model results. Our analysis suggests a three-step mechanism leading to this event:(1) development of an easterly low-level wind along the Gangetic Plain caused by a low pressure system over the central Gangetic Plain; (2) convergence of moisture over the north-western part of India, leading to an increase of potential instability of the air mass along the valley recesses, which is capped by an inversion located above the ridgeline; and (3) strengthening of the north-westerly flow above the ridges, which supports the lifting of the potentially unstable air over the protruding ridge of the foothills of the Himalayas and triggers shallow convection, which on passing through adjacent folds initiates deep convection.

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Section: Mechanism Of Convection Initiation At Ukhimath Tehsilsupporting

confidence: 92%

Improved understanding of an extreme rainfall event at the Himalayan foothills – a case study using COSMO

Shrestha

Dimri

Schomburg

et al. 2015

Tellus A: Dynamic Meteorology and Oceanography

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“…However, the inconsistency in the timing and duration of the Holocene climatic optimum indicates the occurrence of local variations in rainfall amount in response to the ISM (Bird et al, 2014), which is compatible with the complex terrain of the margin of the QTP. The topography effect of the Tibetan Plateau affects the moisture transfer path and establishes unstable potential energy stratification (Chen et al, 2007;Houze, 2012). The steep terrain of the margin of the QTP strengthens ascending air motions, promoting the release of latent heat and the rapid development of strong convection.…”

Section: Structure Of the Holocene Climatic Optimummentioning

confidence: 99%

Holocene Asian monsoon evolution revealed by a pollen record from an alpine lake on the southeastern margin of the Qinghai–Tibetan Plateau, China

et al. 2016

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Abstract. We present the results of pollen analyses from a 1105 cm long sediment core from Wuxu Lake in southwestern China, which depict the variations of the East Asian winter monsoon (EAWM) and the Indian summer monsoon (ISM) during the last 12.3 ka. During the period of 12.3 to 11.3 cal ka BP, the dominance of Betula forest and open alpine shrub and meadow around Wuxu Lake indicates a climate with relatively cold winters and dry summers, corresponding to the Younger Dryas event. Between 11.3 and 10.4 cal ka BP, further expansion of Betula forest and the retreat of alpine shrubs and meadows reflect a greater seasonality with cold winters and gradually increasing summer precipitation. From 10.4 to 4.9 cal ka BP, the dense forest understory, together with the gradual decrease in Betula forest and increase in Tsuga forest, suggest that the winters became warmer and summer precipitation was at a maximum, corresponding to the Holocene climatic optimum. Between 4.9 and 2.6 cal ka BP, Tsuga forest and alpine shrubs and meadows expanded significantly, reflecting relatively warm winters and decreased summer precipitation. Since 2.6 cal ka BP, reforestation around Wuxu Lake indicates a renewed humid period in the late Holocene; however, the vegetation in the catchment may also have been affected by grazing activity during this period. The results of our study are generally consistent with previous findings; however, the timing and duration of the Holocene climatic optimum from different records are inconsistent, reflecting real contrast in local rainfall response to the ISM. Overall, the EAWM is broadly inphase with the ISM on the orbital timescale, and both monsoons exhibit a trend of decreasing strength from the early to late Holocene, reflecting the interplay of solar insolation receipt between the winter and summer seasons and El Niño-Southern Oscillation strength in the tropical Pacific.

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“…2 and 4). Above 3300 m, the reduced lift over flatter terrain, the exhaustion of precipitable water as storms rise less steeply, and the horizontal displacement of falling snow likely all contribute to declining precipitation at the higher elevations (Mott et al, 2014;Houze Jr., 2012). These processes have been approximated in the Sierra Nevada through simulations based on the convergence of the boundary layer and slope of the local terrain but, until now, have been difficult to observe (Alpert, 1986).…”

Section: Variability Of Orographic Trendsmentioning

confidence: 99%

LiDAR measurement of seasonal snow accumulation along an elevation gradient in the southern Sierra Nevada, California

Kirchner

Bales

Molotch

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. We present results from snow-on and snow-off airborne-scanning LiDAR measurements over a 53 km 2 area in the southern Sierra Nevada. We found that snow depth as a function of elevation increased approximately 15 cm per 100 m, until reaching an elevation of 3300 m, where depth sharply decreased at a rate of 48 cm per 100 m. Departures from the 15 cm per 100 m trend, based on 1 m elevation-band means of regression residuals, showed slightly less steep increases below 2050 m; steeper increases between 2050 and 3300 m; and less steep increases above 3300 m. Although the study area is partly forested, only measurements in open areas were used. Below approximately 2050 m elevation, ablation and rainfall are the primary causes of departure from the orographic trend. From 2050 to 3300 m, greater snow depths than predicted were found on the steeper terrain of the northwest and the less steep northeast-facing slopes, suggesting that ablation, aspect, slope and wind redistribution all play a role in local snow-depth variability. At elevations above 3300 m, orographic processes mask the effect of wind deposition when averaging over large areas. Also, terrain in this basin becomes less steep above 3300 m. This suggests a reduction in precipitation from upslope lifting and/or the exhaustion of precipitable water from ascending air masses. Our results suggest a cumulative precipitation lapse rate for the 2100-3300 m range of about 6 cm per 100 m elevation for the accumulation period of 3 December 2009 to 23 March 2010. This is a higher gradient than the widely used PRISM (Parameter-elevation Relationships on Independent Slopes Model) precipitation products, but similar to that from reconstruction of snowmelt amounts from satellite snow-cover data. Our findings provide a unique characterization of the consistent, steep average increase in precipitation with elevation in snow-dominated terrain, using high-resolution, highly accurate data and highlighs the importance of solar radiation, wind redistribution and mid-winter melt with regard to snow distribution.

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Orographic effects on precipitating clouds

Cited by 645 publications

References 224 publications

Improved understanding of an extreme rainfall event at the Himalayan foothills – a case study using COSMO

Improved understanding of an extreme rainfall event at the Himalayan foothills – a case study using COSMO

Holocene Asian monsoon evolution revealed by a pollen record from an alpine lake on the southeastern margin of the Qinghai–Tibetan Plateau, China

LiDAR measurement of seasonal snow accumulation along an elevation gradient in the southern Sierra Nevada, California

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