From weather to climate—Seasonal and interannual variability of storms and implications for erosion processes in the Himalaya

Abstract

The extent to which orography may be a product of climate-erosion interactions is largely unknown. One grand challenge is to quantify the precipitation regimes of mountainous regions at the spatial and temporal scales relevant for investigating the interplay of erosion and tectonics in active orogens. In this paper, our objective is to synthesize recent research integrating numerical model simulations, satellite data, and surface observations in the Himalaya to elucidate the role of weather and climate in mountain evolution. We focus on the seasonal and interannual space-time variability of precipitation in the Great Himalayas by studying two preeminent storm regimes in detail-monsoon onsets and depressions in general, and wintertime Western Disturbances (cold season events). High-resolution simulations of heavy precipitation storms for two monsoon onset conditions (1999 and 2001) and one wintertime storm (2000) are used to illustrate the complex patterns of interaction between the mountains and the atmosphere, and to show how these affect the spatial distribution of precipitation. Along with observations from an existing ground-based network, these simulations provide unique insights into the space-time features of seasonal and interannual variability of precipitation. Our analysis indicates that the trajectory of monsoon storms during onset events exerts a strong control on the precipitation amounts and rainfall penetration into the rain shadow. Spatial variability of subsequent storm tracks in any given year helps explain the interannual variability of monsoon pre-north-south oriented ridges, forced lifting of moist air enhances precipitation on the

Winter westerly disturbance dynamics and precipitation in the western Himalaya and Karakoram: a wave-tracking approach

“…The product combines TRMM 2B31, TRMM 2A12, special sensor microwave imager, advanced microwave scanning radiometer, advanced microwave sounding unit, and Climate Prediction Center infrared observations to estimate precipitation over low/mid-latitudes and is calibrated by station data. TRMM has documented deficiencies in capturing snowfall, which are especially problematic in HMA during winter (Lang and Barros 2004;Barros et al 2006;Maussion et al 2014). Because accurately quantifying total precipitation accumulation is difficult, our focus is on the timing and the relative precipitation contribution of WWD events, compared to all other dates.…”

“…The link between the atmosphere and glacial trends has also motivated studies on wintertime climate variability (Archer and Fowler 2004;Bhutiyani et al 2010;Dimri and Dash 2012;Palazzi et al 2013). In the KH, an excess of 50 % of the total annual precipitation is delivered by only a few westerly disturbances occurring between the months of December and March (Barros et al 2006). Winter westerly disturbances (WWD) are characteristically eastward propagating extratropical cyclones (Lang and Barros 2004;Barlow et al 2005).…”

Multi-annual variations in winter westerly disturbance activity affecting the Himalaya

“…This was also observed in the CH composite, where moisture-laden flow from the Arabian Sea and Bay of Bengal encountered topography at near right angles. Barros et al (2006) showed through numerical simulation that low-level moisture laden flow approaching the CH lifts orographically to produce strong precipitation at steep angles of incidence.…”

“…TRMM provides near-global 0.25° resolution precipitation estimates at 3-h intervals for the period (Huffman et al 2007Bookhagen 2010 Barros et al 2006). This inability to measure snowfall is particularly problematic for our study given that we are investigating high elevations during winter.…”

“…Furthermore, the blocking of flows associated with these events exhibits complex channelization. Numerical simulation in Barros et al (2006) indicated that river valleys serve as open conduits for moisture into the lee of the incident topography during depressions affecting the CH. Lang and Barros (2004) investigated atmospheric depression's effects on snowfall totals in the CH.…”