The days of plenty might soon be over in glacierized Central Asian catchments

Despite the fact that the fast-growing population of Central Asia strongly depends on glacial melt water for fresh water supply, irrigation and hydropower production, the impact of glacier shrinkage on water availability remains poorly understood. With an annual area loss of 0.36 to 0.76%, glaciers are retreating particularly fast in the northern Tien Shan, thus causing concern about future water security in the densely populated regions of Bishkek and Almaty. Here, we use exceptionally long in-situ data series to run and calibrate a distributed glacio-hydrological model, which we then force with downscaled data from phase five of the Climate Model Intercomparison Project CMIP5. We observe that even in the most glacier-friendly scenario, glaciers will lose up to two thirds (−60%) of their 1955 extent by the end of the 21st century. The range of climate scenarios translates into different changes in overall water availability, from peak water being reached in the 2020s over a gradual decrease to status quo until the end of the 21st century. The days of plenty, however, will not last much longer, as summer runoff is projected to decrease, independent of scenario uncertainty. These results highlight the need for immediate planning of mitigation measures in the agricultural and energy sectors to assure long-term water security in the densely populated forelands of the Tien Shan

Multi-decadal observations in the Alps reveal less and wetter snow, with increasing variability

Snowpack is an important temporal water storage for downstream areas, a potential source of natural hazards (avalanches or floods) and a prerequisite for winter tourism. Here, we use thousands of manual measurements of the water equivalent of the snow cover (SWE) from almost 30 stations between 1,200 and 2,900 m a.s.l. from four long-term monitoring programs (earliest start in 1937) in the center of the European Alps to derive daily SWE based on snow depth data for each station. The inferred long-term daily SWE time series were analyzed regarding spatial differences, as well as potential temporal changes in variability and seasonal averages during the last 7 decades (1957–2022). The investigation based on important hydro-climatological SWE indicators demonstrates significant decreasing trends for mean SWE (Nov-Apr) and for maximum SWE, as well as a significantly earlier occurrence of the maximum SWE and earlier disappearance of the continuous snow cover. The anomalies of mean SWE revealed that the series of low-snow winters since the 1990s is unprecedented since the beginning of measurements. Increased melting during the accumulation period below 2000 m a.s.l is also observed–especially in the most recent years–as well as slower melt rates in spring, and higher day-to-day variability. For these trends no regional differences were found despite the climatological variability of the investigated stations. This indicates that the results are transferable to other regions of the Alps

The rainy season in the Southern Peruvian Andes: A climatological analysis based on the new Climandes index

The rainy season is of high importance for livelihoods in the Southern Peruvian Andes (SPA), especially for agriculture, which is mainly rain fed and one of the main income sources in the region. Therefore, knowledge and predictions of the rainy season such as its onset and ending are crucial for planning purposes. However, such information is currently not readily available for the local population. Moreover, an evaluation of existing rainy season indices shows that they are not optimally suited for the SPA and may not be directly applicable in a forecasting context. Therefore, we develop a new index, named Climandes index, which is tailored to the SPA and designed to be of use for operational monitoring and forecasting purposes. Using this index, we analyse the climatology and trends of the rainy season in the SPA. We find that the rainy season starts roughly between September and January with durations between 3 and 8 months. Both onset and duration show a pronounced northeast-southwest gradient, regions closer to the Amazon Basin have a considerably longer rainy season. The inter-annual variability of the onset is very high, that is, 2–5 months depending on the station, while the end of the rainy season shows a much lower variability (i.e., 1.5–3 months). The spatial patterns of total precipitation amount and dry spells within the rainy season are only weakly related to its timing. Trends in rainy season characteristics since 1965 are mostly weak and not significant, but generally indicate a tendency towards a shortening of the rainy season in the whole study area due to a later onset and an increase in precipitation sums during the rainy season in the northwestern study area

A combined view on precipitation and temperature climatology and trends in the southern Andes of Peru

In the southern Peruvian Andes, communities are highly dependent on climatic conditions due to the mainly rain-fed agriculture and the importance of glaciers and snow melt as a freshwater resource. Longer-term trends and year-to-year variability of precipitation or temperature severely affect living conditions. This study evaluates seasonal precipitation and temperature climatologies and trends in the period 1965/66–2017/18 for the southern Peruvian Andes using quality-controlled and homogenized station data and new observational gridded data. In this region, precipitation exhibits a strong annual cycle with very dry winter months and most of the precipitation falling from spring to autumn. Spatially, a northeast–southwest gradient in austral spring is observed, related to an earlier start of the rainy season in the northeastern partof the study area. Seasonal variations of maximum temperature are weak withan annual maximum in austral spring, which is related to reduced cloud coverin austral spring compared to summer. On the contrary, minimum tempera-tures show larger seasonal variations, possibly enhanced through changes inlongwave incoming radiation following the precipitation cycle. Precipitationtrends since 1965 exhibit low spatial consistency except for austral summer,when in most of the study area increasing precipitation is observed, and in aus-tral spring, when stations in the central-western region of the study area regis-ter decreasing precipitation. All seasonal and annual trends in maximum temperature are larger than trends in minimum temperature. Maximum temperature exhibits strong trends in austral winter and spring, whereas minimum temperature trends are strongest in austral winter. We hypothesize, that these trends are related to precipitation changes, as decreasing (increasing) precipita-tion in spring (summer) may enhance maximum (minimum) temperature trends through changes in cloud cover. El Niño Southern Oscillation (ENSO), however, has modifying effects onto precipitation and temperature, and thereby leads to larger trends in maximum temperatures

SolSeasStore : saisonale Wärmespeicherung in städtischen Quartieren mit Erdwärmesonden

Es wurde untersucht, inwieweit eine Regeneration von Erdwärmesonden (EWS) in dicht besiedelten Gebieten mittels Solarthermie möglich ist, wenn ein gesamtes Wohnquartier durch Wärmepumpen mit EWS beheizt werden soll. Am Beispiel eines typischen Gebäudes mit herausfordernder Regeneration erfolgte zudem eine Betrachtung zusätzlicher Wärmequellen sowie des Stromverbrauches über 50 Jahre. Als Wärmequelle für die Regeneration wurden unabgedeckte PVT- sowie Flachkollektoren verwendet. PVT-Fassadenanlagen, Luft-Wasser-Wärmeübertrager (LWWÜ) als auch die Gebäudekühlung dienten als zusätzliche Wärmequellen. Sofern grosse Gebäude mit hohem Wärmebedarf und verhältnismässig kleiner Dachfläche gleichmässig verteilt sind, ist eine nachhaltige Wärmeversorgung mit regenerativen EWS in suburbanen Quartieren mittels Solarthermie auf den Dächern möglich. In urbanen Quartieren hingegen, in denen Ansammlung grosser Gebäude zu erwarten sind, ist eine ausreichende und rein solarthermische Regeneration nicht möglich. Der Einsatz zusätzlicher Wärmequellen ist in diesen Fällen nötig, um den Regenerationsanteil bei grossen Gebäuden für einen nachhaltigen Betrieb ausreichend anzuheben. Das Projekt wurde vom BFE gefördert: BFE F&E-Projekt SI/501950 (Bearbeitung 2019 – 2021

A new climate and glacier baseline for the Cordillera Vilcanota, Peru, reduces critical information gaps

The Cordillera Vilcanota in the Southern Peruvian Andes is the second largest ice-covered Cordillera in Peru (after the Cordillera Blanca) and serves for the Cusco Region as a temporary water storage for fresh-water and hydropower generation and irrigation. Despite the Cordillera Vilcanota’s size and socio-economic relevance, there has so far no comprehensive baseline data been available for climate and glacier evolution. In the framework of two jointly launched –Peruvian-Swiss climate change impact and adaptation programs (Climate Change Adaptation Programm - PACC; Glacier Change Adaptation and Desaster Risk Reduction Programm - Glacier 513) significant efforts have been undertaken and are on the way to create a climate, glacier and hazard baseline for the Cordillera Vilcanota. Because of the remoteness of the area and the scarcity of available data, multiple sources such as climate stations, climate reanalysis and satellite data have been collected, processed and analyzed

Can we use TRMM-PR bright band heights to estimate the snow-rain transition in high mountain regions?

Field and modelling based research indicates that for tropical glaciers, variations in snow cover and the altitude of the snow line via albedo effects are among the most crucial factors to explain the differences in annual glacier mass balance variability. It is therefore essential to identify the height of the phase change during precipitation events and its coupling with glacier mass balance. This knowledge is also fundamental to assess possible future impacts of e.g. changing air temperatures on glacier mass balances at low latitudes. However, the knowledge on heights of phase changes and air temperature during precipitation events is severely limited by the small number of meteorological measurements at high altitudes in the tropics and the Himalaya. Additionally, their one-dimensional type of observation that cannot appropriately account for the variations along the vertical dimension. Remote sensing data are promising tools to fill these data gaps. Before using remote sensing products for studying surface processes, it is crucial to know their accuracies and limitations. Here, we use the the bright band (BB) calulation of the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) as provided in the product 2A23. The bright band is a horizontal layer of stronger radar reflectivity produced by the melting of precipitation at the level where solid precipitation turns into rain. It may be thus a good proxy for the snowline during precipitation events at high mountain regions. To our knowledge, the potential of this product in studies of glacier surface processes has not been further evaluated so far

Air temperature, radiation budget and area changes of Quisoquipina glacier in the Cordillera Vilcanota (Peru)

The Peruvian Andes host about 71% of all tropical glaciers. Although several studies have focused on glaciers of the largest glaciered mountain range (Cordillera Blanca), other regions have received little attention to date. In 2011, a new program has been initiated with the aim of monitoring glaciers in the centre and south of Peru. The monitoring program is managed by the Servicio Nacional de Meteorología e Hidrología del Perú (SENAMHI) and it is a joint project together with the Universidad San Antonio Abad de Cusco (UNSAAC) and the Autoridad Nacional del Agua (ANA). In Southern Peru, the Quisoquipina glacier has been selected due to its representativeness for glaciers in the Cordillera Vilcanota considering area, length and orientation. The Cordillera Vilcanota is the second largest mountain range in Peru with a glaciated area of approximately 279 km2 in 2009. Melt water from glaciers in this region is partly used for hydropower in the dry season and for animal breeding during the entire year. Using Landsat 5 images, we could estimate that the area of Quisoquipina glacier has decreased by approximately 11% from 3.66 km2 in 1990 to 3.26 km2 in 2010. This strong decrease is comparable to observations of other tropical glaciers

Present and future water resources supply and demand in the Central Andes of Peru: a comprehensive review with focus on the Cordillera Vilcanota

Glaciers have been an important element of Andean societies and livelihoods as direct freshwater supply for agriculture irrigation, hydropower generation and mining activities. Peru’s mainly remotely living population in the Central Andes has to cope with a strong seasonal variation of precipitations and river runoff interannually superimposed by El Niño impacts. Direct glacier and lake water discharge thus constitute a vital continuous water supply and represent a regulating buffer as far as hydrological variability is concerned. This crucial buffer effect is gradually altered by accelerated glacier retreat which leads most likely to an increase of annual river runoff variability. Furthermore, a near-future crossing of the ‘peak water’ is expected, from where on prior enhanced streamflow decreases and levels out towards a new still unknown minimum discharge. Consequently, a sustainable future water supply especially during low-level runoff dry season might not be guaranteed whereas Peru’s water demand increases significantly