Stepwise Onset of Monsoon Weather Observed in the Nepal Himalaya

AbstractMountain weather changes in the Nepal Himalaya were intensively examined during the 2003 monsoon onset using in situ datasets, observed by multiple automatic weather stations (AWS) distributed across the Coordinated Enhanced Observing Period (CEOP) Himalaya reference site at locations with significant differences in altitude. Onset of monsoon rainfall characterized as nighttime precipitation was initiated simultaneously at all stations with the occurrence and migration of a monsoon depression in the north of the Bay of Bengal. Satellite infrared images detected evident suppression of diurnal cloud development after the onset. About two weeks prior to the onset, the mountain weather abruptly changed such that the daytime valley wind at lower elevations weakened associated with morning clouds and the nighttime southerly wind began at upper elevations. The timing corresponded with the weakening of the westerly wind over the Himalaya due to the northward shift of the upper subtropical jet stream. The time lag between the precipitation onset and the change in the mountain weather was confirmed by 9 yr of in situ AWS data. The mechanism of nighttime southerly winds at high elevations is also discussed in relation to large-scale monsoon flow and local circulation

Glacier surface-area changes in Sagarmatha national park, Nepal, in the second half of the 20th century, by comparison of historical maps

AbstractWe investigate variations in the surface area of glaciers in Sagarmatha national park, Nepal, during the second half of the 20th century through comparison of a map applicable to the late 1950s with the official map of Nepal in the early 1990s. The comparison reveals a slight overall decrease in glacier area (by 4.9%, from 403.9 to 384.6 km2), a result which, though potentially subject to errors arising from cartographic interpretation, is in line with the area reductions found by other studies of Asian glaciers. We find that the areas of some individual glaciers, the largest situated at higher altitudes, increased during the study period. This was most apparent for the glaciers oriented to the south, with the increase occurring mainly in the glacier accumulation zones while the fronts tended to recede. Meanwhile, the smaller glaciers, situated lower and on steep basins, experienced a reduction. For the smaller glaciers, the sections most affected by change were the accumulation zones, and these glaciers showed a tendency for the front to advance. In this region there is a lack of climate data for high altitudes. Nevertheless, observations from stations situated around the park suggest that, alongside temperature variations which are often considered the primary factor eliciting glacier response, changes in precipitation play a significant role

Ice ablation and meteorological conditions on the debris-covered area of Baltoro glacier, Karakoram, Pakistan

AbstractDuring the recent Italian expedition 'K2 2004 – 50 years later' (June–July 2004) on Baltoro glacier, Karakoram, Pakistan, glaciological field experiments were carried out on the debris-covered area of this high-elevation glacier. The aim was to investigate the ice ablation and its relations with debris thermal properties and meteorological conditions. Ablation measurements along the glacier up to about 5000 m and within a dedicated test field were combined with meteorological data from two automatic weather stations located at Urdukas (4022 ma.s.l.) and at K2 Base Camp (5033 m a.s.l.). In addition, temperature measurements of the debris cover at different depth levels along the glacier allowed the calculation of debris surface temperature and of the debris thermal resistance (R). Using the air temperature, the local mean lapse rate (0.0075˚C m−1) and the measured ablation, the degree-day factors (K) at different locations on the glacier were calculated. The ice ablation rates were related to debris thickness and elevation. They are typically on the order of 4 cm d−1 during the observation period. However, it was found that the surface topography (slope, aspect) has an influence on the total ablation similar to that of the debris thickness. Thermal resistance of the debris cover and its distribution over the glacier were estimated. Finally, a best-guess estimate of the total meltwater production was calculated from available climate data

Spatial distribution of debris thickness and melting from remote-sensing and meteorological data, at debris-covered Baltoro glacier, Karakoram, Pakistan

AbstractA distributed surface energy-balance study was performed to determine sub-debris ablation across a large part of Baltoro glacier, a wide debris-covered glacier in the Karakoram range, Pakistan. The study area is ~124km2. The study aimed primarily at analyzing the influence of debris thickness on the melt distribution. The spatial distribution of the physical and thermal characteristics of the debris was calculated from remote-sensing (ASTER image) and field data. Meteorological data from an automatic weather station at Urdukas (4022ma.s.l.), located adjacent to Baltoro glacier on a lateral moraine, were used to calculate the spatial distribution of energy available for melting during the period 1–15 July 2004. The model performance was evaluated by comparisons with field measurements for the same period. The model is reliable in predicting ablation over wide debris-covered areas. It underestimates melt rates over highly crevassed areas and water ponds with a high variability of the debris thickness distribution in the vicinity, and over areas with very low debris thickness (<0.03 m). We also examined the spatial distribution of the energy-balance components (global radiation and surface temperature) over the study area. The results allow us to quantify, for the study period, a meltwater production of 0.058 km3

Factors controlling the accelerated expansion of Imja Lake, Mount Everest region, Nepal

This study explores the link between area increase of Imja Tsho (Lake) and changes of Imja Glacier (area ∼25km2) under the influence of climate change using multitemporal satellite imagery and local climate data. Between 1962 and 2013, Imja Lake expanded from 0.03±0.01 to 1.35±0.05 km2 at a rate of 0.026±0.001 km2 a-1. The mean glacier-wide flow velocity was 37±30ma-1 during 1992-93 and 23±15ma-1 during 2013-14, indicating a decreasing velocity. A mean elevation change of -1.29±0.71ma-1 was observed over the lower part of the glacier in the period 2001-14, with a rate of -1.06±0.63ma-1 in 2001-08 and -1.56±0.80ma-1 in 2008-14. We conclude that the decrease in flow velocity is mainly associated with reduced accumulation due to a decrease in precipitation during the last few decades. Furthermore, glacier ablation has increased due to increasing maximum temperatures during the post-monsoon months. Decreased glacier flow velocities and increased mass losses induce the formation and subsequent expansion of glacial lakes under favourable topographic conditions.Publisher PDFPeer reviewe

Protocollo per il campionamento di fitoplancton in ambiente lacustre

No abstract availabl

Trophic condition of the volcanic Lake Nemi (Central Italy): environmental factors and planktonic communities in a changing environment

Lake Nemi is an interesting case of anthropogenic overexploitation which has caused its progressive environmental deterioration in the past decades. On this lake historical data about the trophic situation are available from 1975 to 1984. The research performed in 2002-03, about ten years after the diversion of urban waste waters, concerned a biological investigation on the phyto- and zooplanktonic communities, integrated with a physico-chemical analysis. The aims of our study are to evaluate the current water quality of the lake and compare it with the water quality observed in 1982-1983, when all biotic and abiotic components indicated a heavily compromised hypereutrophic condition. The water quality data and the comparison with a previous study point out that the biological aspects have partially changed (increased number of Cyanobacteria and phytoplanktonic taxa, particularly Clorophyta and Dinophyta; zooplankton composition changed at a species level, with the appearance of taxa associated to light trophic conditions), and the physico-chemical conditions significantly improved. The mean transparency, dissolved oxygen, nutrients and chlorophyll-a concentrations have all improved. Mean annual temperature at different depths increased, probably due to differences in climatic period and the lowering of the lake surface level (from 32.5 to 27.5 m in 1982 and 2002, respectively). Our results indicate a general improving trend in water quality is taking place since the diversion of waste water discharges. The present abiotic characteristics of the lake allow the phytoplankton to distribute itself in the whole epilimnion, and the zooplankton in the whole water column. A possible further improvement is hypothesized, and the constraints represented by excessive water level lowering and water temperature increasing are also discussed

Protocollo di campionamento di macrofite acquatiche in ambiente lacustre

No abstract availableIl presente rapporto descrive la procedura per effettuare il corretto campionamento delle macrofite in ambiente lacustre, allo scopo di impiegare i dati ottenuti per una valutazione di qualit? ecologica dei laghi, secondo quanto previsto dalla Direttiva Comunitaria 2000/60

Protocollo per il campionamento dei parametri chimico-fisici a sostegno degli elementi biologici in ambiente lacustre

Abstract not availableIl protocollo sul campionamento delle acque lacustri integra completandole le metodologie di campionamento ed analisi del fitoplancton, delle macrofite acquatiche e della fauna a macroinvertebrati in ambiente lacustre riportati nei capitoli successivi di questo Manuale. Anche questo protocollo come i precedenti segue le indicazioni della Direttiva 60/2000/CE (Water Framework Directive, WFD) e del Regolamento per la progettazione del programma di monitoraggio emanato dal Ministero dell?Ambiente e della Tutela del Territorio e del Mare