Seasonality and spatial variability of dynamic precipitation controls on the Tibetan Plateau

The Tibetan Plateau (TP) is the origin of many large Asian rivers, which provide water resources for large regions in south and east Asia. Therefore, the water cycle on the TP and adjacent high mountain ranges, in particular the precipitation distribution and variability play an important role for the water availability for billions of people in the downstream regions of the TP. The High Asia Refined analysis (HAR) is used to analyse the dynamical factors that influence precipitation variability in the TP region, including the factors resulting in the enhancement and suppression of precipitation. Four dynamical fields that can influence precipitation are considered: the 300 hPa wind speed and wind speed 2 km above ground, the 300 hPa vertical wind speed, and the atmospheric water transport. The study focusses on the seasonality and the spatial variability of the precipitation controls and their dominant patterns. Results show that different factors have different effects on precipitation in different regions and seasons. This depends mainly on the dominant type of precipitation, i.e. convective or frontal/cyclonic precipitation. Additionally, the study reveals that the midlatitude westerlies have a high impact on the precipitation distribution on the TP and its surroundings year-round and not only in winter

Editorial: Urban climate and heat stress - Part 1

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Editorial: Urban climate and heat stress – Part 2

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Snowmelt and slush avalanches / slushflows in nothern mountains, Sweden. A video presentation.

A video of 15 minutes duration reviews different cases of slushflows in May-June 1995 and their behaviour during release and downslope propagation. Slushflow dynamics are compared with other types of mass movement

Survival of the Qaidam mega-lake system under mid-Pliocene climates and its restoration under future climates

The Qaidam Basin in the north of the Tibetan Plateau has undergone drastic environmental changes during the last millions of years. During the Pliocene, the Qaidam Basin contained a freshwater mega-lake system although the surrounding regions showed increasingly arid climates. With the onset of the Pleistocene glaciations, lakes began to shrink and finally disappeared almost completely. Today, hyperarid climate conditions prevail in the low-altitude parts of the Qaidam Basin. The question of how the mega-lake system was able to withstand the regional trend of aridification for millions of years has remained enigmatic so far. This study reveals that the mean annual water balance, i.e. the mean annual change in terrestrial water storage in the Qaidam Basin, is nearly zero under present climate conditions due to positive values of net precipitation in the high mountain ranges and shows positive annual values during warmer, less dry years. This finding provides a physically based explanation for how mid-Pliocene climates could have sustained the mega-lake system and that near-future climates not much different from present conditions could cause water storage in reservoirs, raising lake levels and expanding lake areas, and may even result in restoration of the mega-lake system over geological timescales. The study reveals that a region discussed as being an analogue to Mars due to its hyperarid environments is at a threshold under present climate conditions and may switch from negative values of long-term mean annual water balance that have prevailed during the last 2.6 million years to positive ones in the near future.TU Berlin, Open-Access-Mittel – 2020BMBF, 03G0804A, Verbundprojekt: WTZ Zentralasien WET; Variabilität und Trends der Wasserhaushaltskomponenten in Benchmark-Einzugsgebieten des Tibet-Plateaus; Leitantrag; Vorhaben: TP1 Atmosphärische ModellierungBMBF, 03G0863C, Verbundprojekt: WTZ Zentralasien CAME II: Q-TiP - Kipp-Punkte von Seesystemen in der ariden Zone Zentralasiens; Vorhaben: Sensitivitätsanalysen zur Wasserbilanz des Qaidam-Beckens (TP 2)DFG, 69015136, Dynamic Response of Glaciers on the Tibetan Plateau to Climate Change - Phase III (DynRG-TiP-III

Occurrence and Coupling of Heat and Ozone Events and Their Relation to Mortality Rates in Berlin, Germany, between 2000 and 2014

Episodes of hot weather and poor air quality pose significant consequences for public health. In this study, these episodes are addressed by applying the observational data of daily air temperature and ozone concentrations in an event-based risk assessment approach in order to detect individual heat and ozone events, as well as events of their co-occurrence in Berlin, Germany, in the years 2000 to 2014. Various threshold values are explored so as to identify these events and to search for the appropriate regressions between the threshold exceedances and mortality rates. The events are further analyzed in terms of their event-specific mortality rates and their temporal occurrences. The results reveal that at least 40% of all heat events during the study period are accompanied by increased ozone concentrations in Berlin, particularly the most intense and longest heat events. While ozone events alone are only weakly associated with increased mortality rates, elevated ozone concentrations during heat events are found to amplify mortality rates. We conclude that elevated air temperatures during heat events are one major driver for increased mortality rates in Berlin, but simultaneously occurring elevated ozone concentrations act as an additional stressor, leading to an increased risk for the regional population.BMBF, 01LP1602, Verbundprojekt Stadtklima: Dreidimensionale Beobachtung atmosphärischer Prozesse in Städten, Modul B - 3D

Contrasting changes of urban heat island intensity during hot weather episodes

Cities typically exhibit higher air temperatures than their rural surroundings, a phenomenon known as the urban heat island (UHI) effect. Contrasting results are reported as to whether UHI intensity (UHII) is exacerbated or reduced during hot weather episodes (HWEs). This contrast is investigated for a four-year period from 2015 to 2018, utilising a set of observational data from high-quality meteorological stations, as well as from hundreds of crowdsourced citizen weather stations, located in the urban region of Berlin, Germany. It can be shown that if HWEs, defined here as the ten percent hottest days or nights during May–September, are identified via daytime conditions, or by night-time conditions at inner-city sites, then night-time UHII is exacerbated. However, if HWEs are identified via night-time conditions at rural sites, then night-time UHII is reduced. These differences in UHII change can be linked with prevalent weather conditions, namely radiation, cloud cover, wind speed, precipitation, and humidity. This highlights that, beside land cover changes, future changes in weather conditions due to climate change will control UHIIs, and thus heat-stress hazards in cities.BMBF, 01LP1602C , Verbundprojekt Stadtklima: Dreidimensionale Beobachtung atmosphärischer Prozesse in Städten, Modul B - 3DODFG, 322579844, Hitzewellen in Berlin, Deutschland - StadtklimamodifkationenDFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Managing and monitoring sustainable regional devolopment in alpine regions

Alpine landscape always has been affected by human economic activities. Traffic economy, tourism economy and industrial structure dominated by small and medium-sized enterprises have been the drivers of economy development as well as of changes in the alpine landscape throughout the last century. There have been tremendous influences of economic activities on special areas but also on the alpine landscape in general. For years numerous regions have been subjected to a strong structural change. Globalisation leads to an acceleration of this structural change. Also, globalisation leads to a fast transition of companies, branches and economies. This transformation is determined by the conversion of the core elements of economic activities, single companies. Companies and branches of the alpine economy have been affected heavily by this transformation process due to several reasons (former regulation, decline of transport costs, etc.). The regions try to influence the negative effects of this structural change in various ways. The results of their efforts are very different. Some regions manage to improve their economic situation whereas others get worse. It is an open question, which structural and procedural factors are responsible for these differences. There could be a gap between wishful thinking in policy making /development of regional strategies and the possibilities of economic development. All participation processes and works on regional strategies have to be based on a sound understanding of the possibilities to influence the economic development. Regional development has tremendously changed in the past few years. So, the question arises how regions are going to organise and manage their sustainable development in the long run. Therefore, appropriate management tools have to be designed. However the central question of the paper is, how regions manage to remain as attractive living spaces. If we knew, what strategies regions should apply and how they should change their strategies in the light of the growing influence of globalisation, we could be able to develop tools for future regional development, that could take the demands of sustainability better into account. Therefore, the paper focuses on the following four areas: - The long-term changes of the (economic) situation in peripheral regions of the Alps. What have been the most important sources of income/net value creation in the last years? How have factors like income, branches and work force developed? How has the created income and value been distributed to different branches and population groups - The effects of globalisation on relevant branches for peripheral regions (e.g. Tourism, agriculture and forestry, building and industry). Which effects of globalisation have been the most influential ones? What external effects have to be expected in alpine regions through these economic trends? - Evaluation of the regional strategies to cope with economic structural changes. It will be promising to examine the Regional Development Schemes. - Development of a management system for sustainable regional development in peripheral regions, which should be applicable as a standardized tool

WRF‐based dynamical downscaling of ERA5 reanalysis data for High Mountain Asia: Towards a new version of the High Asia Refined analysis

The High Asia Refined analysis (HAR) is a regional atmospheric data set generated by dynamical downscaling of the Final operational global analysis (FNL) using the Weather Research and Forecasting (WRF) model. It has been successfully and widely utilized. A new version (HAR v2) with longer temporal coverage and extended domains is currently under development. ERA5 reanalysis data is used as forcing data. This study aims to find the optimal set‐up for the production of the HAR v2 to provide similar or even better accuracy as the HAR. First, we conducted a sensitivity study, in which different cumulus, microphysics, planetary boundary layer, and land surface model schemes were compared and validated against in situ observations. The technique for order preference by similarity to the ideal solution (TOPSIS) method was applied to identify the best schemes. Snow depth in ERA5 is overestimated in High Mountain Asia (HMA) and causes a cold bias in the WRF output. Therefore, we used Japanese 55‐year Reanalysis (JRA‐55) to correct snow depth initialized from ERA5 based on the linear scaling approach. After applying the best schemes identified by the TOPSIS method and correcting the initial snow depth, the model performance improves. Finally, we applied the improved set‐up for the HAR v2 and computed a one‐year run for 2011. Compared to the HAR, the HAR v2 has a better representation of air temperature at 2 m. It produces slightly higher precipitation amounts, but the spatial distribution of seasonal mean precipitation is closer to observations.BMBF, 03G0878G, Verbundprojekt: CLIENT II - CaTeNA; Klimatische und Tektonische Naturrisiken in Zentralasien; Vorhaben: Klimatische Auslöser von HangrutschungenTU Berlin, Open-Access-Mittel – 202