scholarly journals Radiative cooling by clouds affects the precipitation - temperature scaling derived from observations

2021 ◽  
Author(s):  
Sarosh Alam Ghausi ◽  
Axel Kleidon ◽  
Subimal Ghosh
Keyword(s):  
Extreme Precipitation ◽  
Surface Radiation ◽  
Balance Model ◽  
Atmospheric Conditions ◽  
Precipitation Temperature ◽  
Clear Sky ◽  
Scaling Relationships ◽  
Precipitation Response ◽  
Temperature Scaling ◽  
Precipitation Events

<p>One direct effect of climate warming on hydrology is the increase in moisture holding capacity of atmosphere at the rate of 7%/°C as suggested by the Clausius Clapeyron equation. Extreme precipitation largely depends on the amount of precipitable water in the atmospheric column and is thus expected to scale with temperature at the same rate. Observations, however, show significant variability in precipitation - temperature scaling rates, with negative scaling dominating in the tropical regions. These scaling relationships assume a one way causality, i.e. temperature is independent of precipitation. However, we show here that temperatures strongly co-vary with precipitation through the effect that clouds have on surface radiation. The presence of clouds associated with precipitation events result in lower solar isolation at the surface, further leading to reduced temperatures. This induces a two-way causality and thus temperature is no longer independent of precipitation. To remove this cooling effect of clouds, we used a surface energy balance model with a thermodynamic constraint to derive clear sky temperatures during precipitation events. We then show using observations from India, that extreme precipitation scaled with clear sky temperatures shows an increase consistent with the CC rate. On contrary, the negative scaling obtained using observed temperatures misrepresent the precipitation response to warming as a result of the co-variation with the cloud radiative effect. Our findings reveal that scaling relationships not only show how precipitation changes with temperature but also how atmospheric conditions associated with precipitation affect temperature. Thus, this covariation needs to be taken into account when using observations to derive scaling relationships that are then used to infer the extreme precipitation response to climate change.</p>

scholarly journals Temperature scaling of extreme precipitation events – an application of the new DWD event catalogue

2021 ◽  
Author(s):  
Tanja Winterrath ◽  
Ewelina Walawender ◽  
Katharina Lengfeld ◽  
Elmar Weigl ◽  
Andreas Becker
Keyword(s):  
Extreme Precipitation ◽  
Ambient Air ◽  
Precipitation Intensity ◽  
Convective Precipitation ◽  
Precipitation Event ◽  
Extreme Precipitation Events ◽  
Precipitation Regimes ◽  
Temperature Scaling ◽  
First Results ◽  
Precipitation Events

<p>According to the Clausius-Clapeyron equation on saturation vapour pressure a temperature increase of 1 K allows an atmospheric air mass to hold approximately 7 % more water vapour thus increasing its potential for heavy precipitation. Several published measurement studies on the relation between precipitation intensity and temperature, however, revealed an increase of even up to twofold the CC rate for short-term precipitation events. Model conceptions explain this scaling behaviour with increasing temperature by different intensification pathways of convective processes and/or a transition between stratiform and convective precipitation regimes that both can hardly be verified by point measurements alone. In this presentation, we present first results of the correlation between ambient air temperature and different attributes of the Catalogue of Radar-based Heavy Rainfall Events (CatRaRE) recently published by Deutscher Wetterdienst (DWD). This object-oriented event catalogue files and characterizes extreme precipitation events that have occurred on German territory since 2001. It is based on the high-resolution precipitation climate data set RADKLIM of DWD, i.e. contiguous radar-based reflectivity measurements adjusted to hourly station-based precipitation totals and corrected for typical measurement errors applying specific climatological correction methods. Our analysis gives new insights into potential explanations of the observed temperature scaling relating not only precipitation intensity but characteristic event properties like area, duration, and extremity indices with ambient temperature data. With this approach, extreme precipitation events can be analysed in a comprehensive way that is significant in the context of potential impact. The presented analysis moreover allows testing the hypothesis of regime changing based on objective precipitation event criteria that are typical for different precipitation types. We will briefly present the methodological background of CatRaRE with special focus on the event attributes used in the analysis of Clausius-Clapeyron scaling and give first results on the retrieved temperature dependencies of extreme precipitation events.</p>

scholarly journals More frequent flash flood events and extreme precipitation favouring atmospheric conditions in temperate regions of Europe

2021 ◽  
Author(s):  
Judith Meyer ◽  
Malte Neuper ◽  
Luca Mathias ◽  
Erwin Zehe ◽  
Laurent Pfister
Keyword(s):  
Extreme Precipitation ◽  
Western Europe ◽  
Flash Flood ◽  
Flash Floods ◽  
Water Levels ◽  
Specific Humidity ◽  
Atmospheric Conditions ◽  
Flood Events ◽  
Extreme Precipitation Events ◽  
Precipitation Events

Abstract. In recent years, flash floods repeatedly occurred in temperate regions of central western Europe. Unlike in Mediterranean catchments, this flooding behaviour is unusual. In the past, and especially in the 1990s, floods were characterized by predictable, slowly rising water levels during winter and driven by westerly atmospheric fluxes (Pfister et al., 2004). The intention of this study is to link the recent occurrence of flash floods in central western Europe to extreme precipitation and specific atmospheric conditions to identify the cause for this apparent shift. Therefore, we hypothesise that an increase in extreme precipitation events has subsequently led to an increase in the occurrence of flash flood events in central western Europe and all that being caused by a change in the occurrence of flash flood favouring atmospheric conditions. To test this hypothesis, we compiled data on flash floods in central western Europe and selected precipitation events above 40 mm h−1 from radar data (RADOLAN, DWD). Moreover, we identified proxy parameters representative for flash flood favouring atmospheric conditions from the ERA5 reanalysis dataset. High specific humidity in the lower troposphere (q ≥ 0.004 kg kg−1), sufficient latent instability (CAPE ≥ 100 J kg−1) and weak deep-layer wind shear (DLS ≤ 10 m s−1) proved to be characteristic for long-lasting intense rainfall that can potentially trigger flash floods. These atmospheric parameters, as well as the flash flood and precipitation events were then analysed using linear models. Thereby we found significant increases in atmospheric moisture contents and increases in atmospheric instability. Parameters representing the motion and organisation of convective systems occurred slightly more often or remained unchanged in the time period from 1981–2020. Moreover, a trend in the occurrence of flash floods was confirmed. The number of precipitation events, their maximum 5-minute intensities as well as their hourly sums were however characterized by large inter-annual variations and no trends could be identified between 2002–2020. This study therefore shows that the link from atmospheric conditions via precipitation to flash floods cannot be traced down in an isolated way. The complexity of interactions is likely higher and future analyses should include other potentially relevant factors such as intra-annual precipitation patterns or catchment specific parameters.

Are extreme precipitation events becoming stronger and warmer in the Andes?

2021 ◽  
Author(s):  
Miguel Lagos-Zúñiga ◽  
Pablo A. Mendoza ◽  
Roberto Rondanelli
Keyword(s):  
Air Temperature ◽  
Extreme Precipitation ◽  
High Elevation ◽  
Atmospheric Conditions ◽  
Freezing Level ◽  
The Andes ◽  
Extreme Precipitation Events ◽  
Hydrological Impacts ◽  
Orographic Enhancement ◽  
Precipitation Events

<p>The Andes Cordillera serves as a physical barrier that modulates the atmospheric fluid dynamics, affecting the occurrence and intensity of precipitation events through orographic enhancement and the blocking and deviation of humidity transported by jets. The quantification of extreme precipitation events (EPEs) and their associated temperature is critical to address hydrological impacts and water availability for the Andes that also feeds the majority of the river and population in the region. </p><p>As the atmosphere is getting warmer, the increasing amount of water vapor available in the troposphere is expected to enhance warm precipitation events during the 21st century. In this study, we examine observational trends in extreme precipitation events by season and analyze possible connections with air temperature. To this end, we perform Sen's Tests and compute Mann-Kendall values Maximum Precipitation daily precipitation and its associated temperature at ~80 meteorological stations. Then, we cluster the results geographically finding positive trends in high elevation areas for extreme precipitation events (EPEs) and their temperature, especially in mid-latitudes. In low stations (<800 m a.s.l.), we obtain a decrease in the magnitude of EPEs but and a decrease in air temperature (up to -0.4 [°C/decade]). In general, the temperature increase in EPEs for high elevation stations < 0.12 °C/year and could rise the freezing level up to 1000 [m], during the fall season.  The presented here suggest positive feedback between warmer atmospheric conditions and the open further pathways regarding hydrological impacts such as debris flow, floods, and less snow availability in the Andes regions.</p>

scholarly journals Quality assessment of heterogeneous surface radiation network data

2012 ◽  
Vol 8 (1) ◽  
pp. 93-97 ◽  
Author(s):  
R. Becker ◽  
K. Behrens
Keyword(s):  
Quality Assessment ◽  
Sunshine Duration ◽  
Surface Radiation ◽  
Quality Data ◽  
Atmospheric Conditions ◽  
Remotely Sensed Data ◽  
Clear Sky ◽  
Assessment Approach ◽  
Sensor Degradation ◽  
Cloud Mask

Abstract. The DWD national radiation measurement network comprises 82 automatic sites, 29 manned sites with shaded and unshaded pyranometer and the BSRN station at Lindenberg. The quality assessment routinely applied takes into account the basic astronomical and empirical considerations as well as some interdependencies like total to diffuse flux relation and cross checking with sunshine duration. A more advanced quality assessment approach attempts to routinely utilise timeseries of clear sky radiative transfer simulations for every site. For that purpose a link to cloud coverage obtained from Meteosat second generation geostationary satellite data, highly resolved in time and space, was established. There is a predefined calibration cycle of 30 month for automatic stations. Data analysis on this timescale allows for the detection of sensor degradation, wrong calibration or configuration and other possible local disturbances. Furthermore using satellite cloud mask enables the identification of larger clear sky regions characterized by similar atmospheric conditions. Thus, in a regionalization step correction or recalibration of moderate quality data to a higher level can be considered. The paper provides an overview of DWD surface radiation network and the current activities to improve automatic quality assessment using remotely sensed data and clear sky modeling for the upgrading of radiation data.

Eliminating the “hook” in Precipitation-Temperature Scaling

2021 ◽  
pp. 1-42
Author(s):  
Johan B. Visser ◽  
Conrad Wasko ◽  
Ashish Sharma ◽  
Rory Nathan
Keyword(s):  
Extreme Precipitation ◽  
Precipitation Event ◽  
Rainfall Events ◽  
Precipitation Temperature ◽  
Climatic Regions ◽  
Warming Climate ◽  
Average Precipitation ◽  
Temperature Scaling ◽  
Tropical Climates ◽  
Conditioning Event

AbstractObservational studies of extreme daily and subdaily precipitation-temperature sensitivities (apparent scaling) aim to provide evidence and improved understanding of how extreme precipitation will respond to a warming climate. However, interpretation of apparent scaling results is hindered by large variations in derived scaling rates and divergence from theoretical and modelled projections of systematic increases in extreme precipitation intensities (climate scaling). In warmer climatic regions, rainfall intensity has been reported to increase with temperature to a maximum before decreasing, creating a second order discontinuity or “hook” like structure. Here we investigate spatial and temporal discrepancies in apparent scaling results by isolating rainfall events and conditioning event precipitation on duration. We find that previously reported negative apparent scaling at higher temperatures which creates the hook structure, is the result of a decrease in the duration of the precipitation event, and not to the decrease in precipitation rate. We introduce standardized pooling using long records of Australian station data across climate zones, to show average precipitation intensities and 1-h peak precipitation intensities increase with temperature across all event durations and locations investigated. For shorter duration events (< 6-h), average precipitation intensity scaling is in line with the expected Clausius- Clapeyron (CC) relation at ~7 %/°C, and this decreases with increasing duration, down to 2 %/°C at 24-h duration. Consistent with climate scaling derived from model projections, 1-h peak precipitation intensities are found to increase with temperature at elevated rates compared to average precipitation intensities, with super-CC scaling (10 – 14 %/°C) found for short-duration events in tropical climates.

scholarly journals Atmospheric conditions of extreme precipitation events in western Turkey for the period 2006–2015

2019 ◽  
Vol 19 (1) ◽  
pp. 107-119 ◽  
Author(s):  
Bulent Oktay Akkoyunlu ◽  
Hakki Baltaci ◽  
Mete Tayanc
Keyword(s):  
Extreme Precipitation ◽  
Eastern Mediterranean ◽  
Balkan Peninsula ◽  
Marmara Region ◽  
Atmospheric Conditions ◽  
Pressure Center ◽  
Western Turkey ◽  
Extreme Precipitation Events ◽  
Synoptic Conditions ◽  
Precipitation Events

Abstract. This paper investigates the precipitation types and background physical mechanisms of extreme precipitation events (EPEs) over western Turkey during the period 2006–2015. The EPEs are described as the precipitation values above the 90th percentile obtained from the hourly precipitation dataset, which has high spatial resolution. Precipitation types associated with EPEs are identified by using radar outputs and the Lamb weather type (LWT) approach. It is found that EPEs occurred more frequently in the Marmara and Aegean regions during autumn and winter months. In Marmara, mainly 21 %, 17 %, and 15 % of total autumn EPEs show convective, cyclonic, and sea-effect precipitation characteristics, respectively. While convective EPEs are seen more commonly in the southern portions, cyclonic and sea-effect-originated EPEs mainly affect the southwest and northeastern parts of Marmara. Among these three precipitation types, convective mechanisms generally produce more intense daily precipitation (66.1 mm on average) in the Marmara Region under the proper synoptic conditions (high-pressure center over the Balkan Peninsula and low-pressure center over the eastern Mediterranean). Based on the hourly observations, convective types of extreme precipitation (EP) show two peak values during afternoon and evening times of the day and are linked to diurnal heating. In terms of the Aegean Region, cyclone-originated EP, which includes 65 % of the total winter EPEs, is more common in the whole territory and reaches its peak value during the early hours of the day.

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