Status: this preprint was under review for the journal TC but the revision was not accepted.
Modeling Slope Environmental Lapse Rate (SELR) of temperature
in the monsoon glacio-hydrological regime of the Himalaya
Renoj J. Thayyenand Ashok P. Dimri
Abstract. Moisture, temperature and precipitation interplay forced through the orographic processes sustain and regulate the Himalayan cryospheric system. However, factors influencing the Slope Environmental Lapse Rate (SELR) of temperature along the Himalayan mountain slopes and an appropriate modeling solution remains a key knowledge gap. Present study evaulates the SELR variations in the monsoon regime of the Himalaya and proposes a modeling solution for the valley scale SELR assessment. SELR of selected station pairs in the Sutlej and Beas basins ranging between 662 m a.s.l. to 3130 m a.s.l. and that of Garhwal Himalaya ranging between 2540 m a.s.l. and 3763 m a.s.l. were assessed in this study. Study suggests moisture- temperature interplay is forcing the seasonal as well as elevation depended variability of SELR. SELR constrianed to the nival- glacier regime is found to be comparable with the saturated adiabatic lapse rate (SALR) and lower than the valley scale SELR. Moisture influx to the region, during Indian summer monsoon (ISM) is found to be lowering the seasonal valley scale SELR to SALR levels during July and August months. Highest valley scale SELR was observed in the months of April, May and June, which susequently lowered to the SALR level with the influx of monsoon moisture. This seasonal variability of SELR is found to be closly linked with the variations in the local lifting condensation levels (LCL). Inter-annual variations in SELR of the nival-glacier regime is found to be significant while that of the valley scale SELR is more stable. Hence, it is proposed to use the valley scale SELR for glacier melt/runoff studies. We propose a simple model for deriving the valley scale SELR of monsoon regime using a derivative of the Clausius–Clapeyron relationship. SELR modeling solution is achieved by deriving separate monthly SELR indices from one of the station pairs in the Beas basin from 1986–1990 and sucessfully applied for other select station pairs in Sutlej and Garhwal basins as well as for different time periods. This work emphasis that the arbitary use of temperature lapse rate is extremely untenable in the Himalayan region and significant further research is required to build data and concepts for a comphrehensive atmospheric model valid across the glacio-hydrologic regimes of the Himalaya.
Received: 11 Jun 2016 – Discussion started: 10 Aug 2016
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Present study shows that the seasonal variations in the temperature lapse rate along the Himalayan slopes is dominated by pre-monsoon high and monsoon lows. However, lapse rates restricted to the higher elevation regions did not show this seasonal variation. As the observed lapse rate deviate significantly from standard lapse rate of 6.5 K/km, a modeling solution is proposed by deriving monthly lapse rate indices for improving the snow, glaciers and other modeling effort in the region.
Present study shows that the seasonal variations in the temperature lapse rate along the...
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