scholarly journals Synoptic processes of winter precipitation in the Upper Indus Basin

2021 ◽  
Author(s):  
Jean-Philippe Baudouin ◽  
Michael Herzog ◽  
Cameron A. Petrie
Keyword(s):  
Thermal Structure ◽  
Winter Precipitation ◽  
Indus Basin ◽  
Lower Altitude ◽  
Upper Troposphere ◽  
North West ◽  
Upper Indus Basin ◽  
Western Disturbance ◽  
The North ◽  
Western Disturbances

Abstract. Precipitation in the Upper Indus Basin is triggered by cross-barrier moisture transport. Winter precipitation events are particularly active in this region and are driven by an approaching upper troposphere Western Disturbance. Here statistical tools are used to decompose the winter precipitation timeseries into a wind and a moisture contribution. The relationship between each contribution and the Western Disturbances are investigated. We find that the wind contribution is not only related to the intensity of the upper troposphere disturbances but also to their thermal structure through baroclinic processes. Particularly, a short-lived baroclinic interaction between the Western Disturbance and the lower altitude cross-barrier flow occurs due to the shape of the relief. This interaction explains both the high activity of Western Disturbances in the area, as well as their quick decay as they move further east. We also revealed the existence of a moisture pathway from the Red Sea, to the Persian Gulf and the north of the Arabian Sea. A Western Disturbance strengthens this flow and steers it towards the Upper Indus Plain, particularly if it originates from a more southern latitude. In cases where the disturbance originates from the north-west, its impact on the moisture flow is limited, since the advected continental dry air drastically limits the precipitation output. The study offers a conceptual framework to study the synoptic activity of Western Disturbances as well as key parameters that explain their precipitation output. This can be used to investigate meso-scale processes or intra-seasonal to inter-annual synoptic activity.

scholarly journals Synoptic processes of winter precipitation in the Upper Indus Basin

2021 ◽  
Vol 2 (4) ◽  
pp. 1187-1207
Author(s):  
Jean-Philippe Baudouin ◽  
Michael Herzog ◽  
Cameron A. Petrie
Keyword(s):  
Thermal Structure ◽  
Winter Precipitation ◽  
Indus Basin ◽  
Lower Altitude ◽  
Moisture Flow ◽  
Upper Troposphere ◽  
Upper Indus Basin ◽  
Western Disturbance ◽  
The North ◽  
Western Disturbances

Abstract. Precipitation in the Upper Indus Basin is triggered by orographic interaction and the forced uplift of a cross-barrier moisture flow. Winter precipitation events are particularly active in this region and are driven by an approaching upper-troposphere western disturbance. Here statistical tools are used to decompose the winter precipitation time series into a wind and a moisture contribution. The relationship between each contribution and the western disturbances are investigated. We find that the wind contribution is related not only to the intensity of the upper-troposphere disturbances but also to their thermal structure through baroclinic processes. Particularly, a short-lived baroclinic interaction between the western disturbance and the lower-altitude cross-barrier flow occurs due to the shape of the relief. This interaction explains both the high activity of western disturbances in the area and their quick decay as they move further east. We also revealed the existence of a moisture pathway from the Red Sea to the Persian Gulf and the north of the Arabian Sea. A western disturbance strengthens this flow and steers it towards the Upper Indus Plain, particularly if it originates from a more southern latitude. In cases where the disturbance originates from the north-west, its impact on the moisture flow is limited, since the advected continental dry air drastically limits the precipitation output. The study offers a conceptual framework to study the synoptic activity of western disturbances as well as key parameters that explain their precipitation output. This can be used to investigate meso-scale processes or intra-seasonal to inter-annual synoptic activity.

scholarly journals Effect of tropical cyclones on the Stratosphere-Troposphere Exchange observed using satellite observations over north Indian Ocean

2016 ◽  
Author(s):  
M. Venkat Ratnam ◽  
S. Ravindra Babu ◽  
S. S. Das ◽  
Ghouse Basha ◽  
B. V. Krishnamurthy ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Lower Stratosphere ◽  
North Indian Ocean ◽  
Satellite Observations ◽  
Upper Troposphere ◽  
North West ◽  
The North ◽  
The Impact

Abstract. Tropical cyclones play an important role in modifying the tropopause structure and dynamics as well as stratosphere-troposphere exchange (STE) process in the Upper Troposphere and Lower Stratosphere (UTLS) region. In the present study, the impact of cyclones that occurred over the North Indian Ocean during 2007–2013 on the STE process is quantified using satellite observations. Tropopause characteristics during cyclones are obtained from the Global Positioning System (GPS) Radio Occultation (RO) measurements and ozone and water vapor concentrations in UTLS region are obtained from Aura-Microwave Limb Sounder (MLS) satellite observations. The effect of cyclones on the tropopause parameters is observed to be more prominent within 500 km from the centre of cyclone. In our earlier study we have observed decrease (increase) in the tropopause altitude (temperature) up to 0.6 km (3 K) and the convective outflow level increased up to 2 km. This change leads to a total increase in the tropical tropopause layer (TTL) thickness of 3 km within the 500 km from the centre of cyclone. Interestingly, an enhancement in the ozone mixing ratio in the upper troposphere is clearly noticed within 500 km from cyclone centre whereas the enhancement in the water vapor in the lower stratosphere is more significant on south-east side extending from 500–1000 km away from the cyclone centre. We estimated the cross-tropopause mass flux for different intensities of cyclones and found that the mean flux from stratosphere to troposphere for cyclonic stroms is 0.05 ± 0.29 × 10−3 kg m−2 and for very severe cyclonic stroms it is 0.5 ± 1.07 × 10−3 kg m−2. More downward flux is noticed in the north-west and south-west side of the cyclone centre. These results indicate that the cyclones have significant impact in effecting the tropopause structure, ozone and water vapour budget and consequentially the STE in the UTLS region.

Evaluation of legumes for introduction into native grass pastures on the North-west slopes of New South Wales

1994 ◽  
Vol 34 (4) ◽  
pp. 449 ◽  
Author(s):  
RD FitzGerald
Keyword(s):  
Plant Density ◽  
New South ◽  
New South Wales ◽  
Subterranean Clover ◽  
Soil Types ◽  
Native Grass ◽  
Lower Altitude ◽  
North West ◽  
The North ◽  
South Wales

A range of pasture legumes was either broadcast or drilled into native grass pastures on the North-west Slopes of New South Wales to identify legumes that would persist in that environment and improve the quality of winter pastures based on native grasses. There were 2 experiments conducted over 12 sites. In the first, sites were selected to permit identification of effects of altitude and 2 soil types on legume adaptation. In the second, the lower altitude range was extended and a wider range of soil types was sampled. Subterranean clover (Trifolium subterraneum L.) was the most persistent and productive species, with cultivar performance varying with altitude. At the lowest altitude (340 m) the early-maturing cv. Dalkeith was the most productive, and at 500-600 m there was little difference between the tested cultivars. Stand density, herbage yield, and seed yield all declined as altitude increased, but the decline was greater with earlier maturing cultivars than with the later maturing cv. Woogenellup White clover (T. repens cv. Haifa) established poorly in native grass swards, but plants that did establish persisted during favourable seasons at higher altitudes. Herbage yields of woolly pod vetch (Vicia dasycarpa cv. Namoi) and rose clover (T. hirtum cv. Hykon) occasionally exceeded yield of subterranean clover at some lower altitude sites, but those species failed to persist at other sites where grazing management may have been unsuitable. Barrel medic (Medicago truncatula) established satisfactorily but did not persist on the more acidic soils (pH <6.0). Both drilling and broadcasting establishment techniques produced satisfactory legume stands. Legume plant density was generally greater on heavier soils of basaltic origin than on lighter soils of rhyolitic origin.

scholarly journals Spatial and temporal variations in precipitation in the Upper Indus Basin, global teleconnections and hydrological implications

2004 ◽  
Vol 8 (1) ◽  
pp. 47-61 ◽  
Author(s):  
D.R. Archer ◽  
H.J. Fowler
Keyword(s):  
Climatic Variability ◽  
Regional Scale ◽  
Rural Livelihoods ◽  
Temporal Variations ◽  
Winter Precipitation ◽  
Indus Basin ◽  
Strong Positive Correlation ◽  
Positive Correlation ◽  
Upper Indus Basin ◽  
River Indus

Abstract. Most of the flow in the River Indus from its upper mountain basin is derived from melting snow and glaciers. Climatic variability and change of both precipitation and energy inputs will, therefore, affect rural livelihoods at both a local and a regional scale through effects on summer runoff in the River Indus. Spatial variation in precipitation has been investigated by correlation and regression analysis of long-period records. There is a strong positive correlation between winter precipitation at stations over the entire region, so that, for practical forecasting of summer runoff in some basins, a single valley-floor precipitation station can be used In contrast, spatial relationships in seasonal precipitation are weaker in summer and sometimes significantly negative between stations north and south of the Himalayan divide. Although analysis of long datasets of precipitation from 1895 shows no significant trend, from 1961–1999 there are statistically significant increases in winter, in summer and in the annual precipitation at several stations. Preliminary analysis has identified a significant positive correlation between the winter North Atlantic Oscillation (NAO) and winter precipitation in the Karakoram and a negative correlation between NAO and summer rainfall at some stations. Keywords: upper Indus basin, climate change, time series analysis, spatial correlation, teleconnections

scholarly journals Space-Time Characterization of Rainfall Field in Tuscany

2016 ◽  
Author(s):  
Alessandro Mazza
Keyword(s):  
Kendall Test ◽  
Winter Precipitation ◽  
Rainfall Regime ◽  
North West ◽  
Rain Gauges ◽  
The North ◽  
South Central ◽  
Cumulative Rainfall ◽  
North Eastern

Precipitation during 2001-2016 over the northern and central part of Tuscany was studied in order to characterize the rainfall regime. The dataset consisted of hourly cumulative rainfall series recorded by a network of 801 rain gauges. The territory was divided into 30x30 km square areas, the annual, seasonal and daily Average Cumulative Rainfall (ACR) in all areas was estimated along with its uncertainty. The trend analysis of ACR time series was performed by means of the Mann-Kendall test. Four climatic zones were identified: the north-western was the rainiest, followed by the north-eastern, north-central and south-central. An overall increase in precipitation was identified, more intense in the north-west, and determined mostly by the increase in winter precipitation. On the entire territory, the ACR, number of rainy days, mean precipitation intensity and sum of daily ACR in four intensity groups were evaluated at annual and seasonal scale. The main result was a magnitude of the ACR trend evaluated as 35 mm/year, due mainly to an increase in light and extreme precipitations. This result is in contrast with the decreasing rainfall detected in the past decades.

The relationship of Western Disturbances to precipitation in the upper Indus River basin

2020 ◽  
Author(s):  
Jean-Philippe Baudouin ◽  
Michael Herzog ◽  
Cameron A. Petrie
Keyword(s):  
River Basin ◽  
Arabian Sea ◽  
Heavy Precipitation ◽  
Winter Precipitation ◽  
Precipitation Variability ◽  
Indus River ◽  
Low Level ◽  
Western Disturbance ◽  
Western Disturbances ◽  
Indus River Basin

&lt;p&gt;The upper Indus River basin is characterised by heavy precipitation falling near the foothills of the major mountain ranges, during two wet seasons: winter and summer. Winter precipitation is known to be related to the passing of upper-level synoptic systems embedded in the subtropical westerly jet called Western Disturbances. Here, we investigate the precipitation variability in relation to the Western Disturbances at the synoptic scale, using ERA5 reanalysis data. We take advantage of the results of a previous study that showed that the precipitation is mostly triggered by the forced uplift of a low-level moisture-rich southerly flow across the ranges. We show that the low-level southerly wind triggering the precipitation is produced by the interaction of a Western Disturbance with a baroclinic front located between the Iranian plateau and the Arabian Sea. Ahead of the Western Disturbance, low-level winds draw moisture from the extreme north of the Arabian Sea, the Persian Gulf, and to a lower extent, the Red Sea. At the rear, moisture is depleted by the advection of continental dry air in the Indus River basin. However, the balance between moisture drawing and depletion depends on the characteristics of the Western Disturbance, leading to differences in precipitation intensity. We found the jet position and western Russia blockings to play a role in this. These findings offer clues to understand the longer-term precipitation variability in the area.&lt;/p&gt;

scholarly journals Bacterial GDGTs in Holocene sediments and catchment soils of a high Alpine lake: application of the MBT/CBT-paleothermometer

2012 ◽  
Vol 8 (3) ◽  
pp. 889-906 ◽  
Author(s):  
H. Niemann ◽  
A. Stadnitskaia ◽  
S. B. Wirth ◽  
A. Gilli ◽  
F. S. Anselmetti ◽  
...  
Keyword(s):  
Surface Sediments ◽  
Membrane Lipids ◽  
Winter Precipitation ◽  
Alpine Lake ◽  
Ice Age ◽  
Small Catchment ◽  
North West ◽  
Climate Anomalies ◽  
North East ◽  
The North

Abstract. A novel proxy for continental mean annual air temperature (MAAT) and soil pH, the MBT/CBT-paleothermometer, is based on the temperature (T) and pH-dependent distribution of specific bacterial membrane lipids (branched glycerol dialkyl glycerol tetraethers – GDGTs) in soil organic matter. Here, we tested the applicability of the MBT/CBT-paleothermometer to sediments from Lake Cadagno, a high Alpine lake in southern Switzerland with a small catchment of 2.4 km2. We analysed the distribution of bacterial GDGTs in catchment soils and in a radiocarbon-dated sediment core from the centre of the lake, covering the past 11 000 yr. The distribution of bacterial GDGTs in the catchment soils is very similar to that in the lake's surface sediments, indicating a common origin of the lipids. Consequently, their transfer from the soils into the sediment record seems undisturbed, probably without any significant alteration of their distribution through in situ production in the lake itself or early diagenesis of branched GDGTs. The MBT/CBT-inferred MAAT estimates from soils and surface sediments are in good agreement with instrumental values for the Lake Cadagno region (~0.5 °C). Moreover, downcore MBT/CBT-derived MAAT estimates match in timing and magnitude other proxy-based T reconstructions from nearby locations for the last two millennia. Major climate anomalies recorded by the MBT/CBT-paleothermometer are, for instance, the Little Ice Age (~14th to 19th century) and the Medieval Warm Period (MWP, ~9th to 14th century). Together, our observations indicate the quantitative applicability of the MBT/CBT-paleothermometer to Lake Cadagno sediments. In addition to the MWP, our lacustrine paleo T record indicates Holocene warm phases at about 3, 5, 7 and 11 kyr before present, which agrees in timing with other records from both the Alps and the sub-polar North-East Atlantic Ocean. The good temporal match of the warm periods determined for the central Alpine region with north-west European winter precipitation strength implies a strong and far-reaching influence of the North Atlantic Oscillation on continental European T variations during the Holocene.

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