scholarly journals Persistence of cool conditions after heavy rain in Australia

2018 ◽  
Vol 68 (1) ◽  
pp. 41
Author(s):  
Pandora K. Hope ◽  
Ian G. Watterson
Keyword(s):  
Heavy Rainfall ◽  
Climate Models ◽  
Grid Point ◽  
Heavy Rain ◽  
Daily Minimum Temperature ◽  
Daily Maximum ◽  
The South ◽  
Near Surface ◽  
Almost Everywhere ◽  
Cool Conditions

There is a general understanding that heavy rainfall will suppress subsequent near-surface temperatures. However, there have been few studies describing this effect. In this study the top 10 % of monthly rainfall, by season and by grid point over Australia is used to represent extended periods of heavy rainfall (termed 'very wet'). The corresponding daily maximum average monthly temperature (Tmax) during those months are shown to be cooler by at least 0.5 °C almost everywhere across Australia, in every season in both observation-based data and climate models. Cooler than average Tmax conditions are then evident for the following four months in some places, particularly following very wet months in winter. The average monthly daily minimum temperature (Tmin), unlike Tmax, is warmer than average during very wet months in winter,by up to 1.5 °C in the east of the continent in both observations and the model mean. Warmer Tmin conditions are also evident during very wet months in the south-east and across the south of the continent in other seasons, particularly in observations. Tmin is cooler than average in very wet months in summer elsewhere across the continent. In subsequent months, Tmin then tends to be cooler than average. It is suspected that increased cloud during the first month keeps Tmin warm, while wetter soils contribute to cooler Tmin during subsequent months. These results indicate that indeed heavy, extended rainfall can have a cooling influence on subsequent temperature, and, following winter, this can have an effect right through to the following summer. The Tmax anomalies at the end of the century under RCP8.5 are similar to those under the current climate, except in future there are relatively cooler conditions in the south during very wet months in winter and in the month following.

scholarly journals Joint Occurrence of Daily Temperature and Precipitation Extreme Events over Canada

2014 ◽  
Vol 53 (9) ◽  
pp. 2148-2162 ◽  
Author(s):  
Bárbara Tencer ◽  
Andrew Weaver ◽  
Francis Zwiers
Keyword(s):  
Climate Models ◽  
Regional Climate ◽  
Heavy Precipitation ◽  
Maximum Temperature ◽  
Daily Minimum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
Negative Consequences ◽  
Temperature And Precipitation ◽  
Joint Occurrence

AbstractThe occurrence of individual extremes such as temperature and precipitation extremes can have a great impact on the environment. Agriculture, energy demands, and human health, among other activities, can be affected by extremely high or low temperatures and by extremely dry or wet conditions. The simultaneous or proximate occurrence of both types of extremes could lead to even more profound consequences, however. For example, a dry period can have more negative consequences on agriculture if it is concomitant with or followed by a period of extremely high temperatures. This study analyzes the joint occurrence of very wet conditions and high/low temperature events at stations in Canada. More than one-half of the stations showed a significant positive relationship at the daily time scale between warm nights (daily minimum temperature greater than the 90th percentile) or warm days (daily maximum temperature above the 90th percentile) and heavy-precipitation events (daily precipitation exceeding the 75th percentile), with the greater frequencies found for the east and southwest coasts during autumn and winter. Cold days (daily maximum temperature below the 10th percentile) occur together with intense precipitation more frequently during spring and summer. Simulations by regional climate models show good agreement with observations in the seasonal and spatial variability of the joint distribution, especially when an ensemble of simulations was used.

Assessing the contribution of multiple forcings to changes in temperature extremes 1981–2020 using CMIP6 climate models

2021 ◽  
Author(s):  
Mastawesha Misganaw Engdaw ◽  
Andrew Ballinger ◽  
Gabriele Hegerl ◽  
Andrea Steiner
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Climate Models ◽  
Temporal Trends ◽  
Maximum Temperature ◽  
Daily Minimum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
Temperature Extremes ◽  
Cold Temperatures

<p>In this study, we aim at quantifying the contribution of different forcings to changes in temperature extremes over 1981–2020 using CMIP6 climate model simulations. We first assess the changes in extreme hot and cold temperatures defined as days below 10% and above 90% of daily minimum temperature (TN10 and TN90) and daily maximum temperature (TX10 and TX90). We compute the change in percentage of extreme days per season for October-March (ONDJFM) and April-September (AMJJAS). Spatial and temporal trends are quantified using multi-model mean of all-forcings simulations. The same indices will be computed from aerosols-, greenhouse gases- and natural-only forcing simulations. The trends estimated from all-forcings simulations are then attributed to different forcings (aerosols-, greenhouse gases-, and natural-only) by considering uncertainties not only in amplitude but also in response patterns of climate models. The new statistical approach to climate change detection and attribution method by Ribes et al. (2017) is used to quantify the contribution of human-induced climate change. Preliminary results of the attribution analysis show that anthropogenic climate change has the largest contribution to the changes in temperature extremes in different regions of the world.</p><p><strong>Keywords:</strong> climate change, temperature, extreme events, attribution, CMIP6</p><p> </p><p><strong>Acknowledgement:</strong> This work was funded by the Austrian Science Fund (FWF) under Research Grant W1256 (Doctoral Programme Climate Change: Uncertainties, Thresholds and Coping Strategies)</p>

scholarly journals Assessing the Evolution of Soil Moisture and Vegetation Conditions during a Flash Drought–Flash Recovery Sequence over the South-Central United States

2019 ◽  
Vol 20 (3) ◽  
pp. 549-562 ◽  
Author(s):  
Jason A. Otkin ◽  
Yafang Zhong ◽  
Eric D. Hunt ◽  
Jeff Basara ◽  
Mark Svoboda ◽  
...  
Keyword(s):  
United States ◽  
Soil Moisture ◽  
Land Surface ◽  
Heavy Rainfall ◽  
Recovery Period ◽  
The South ◽  
Recovery Sequence ◽  
Near Surface ◽  
South Central ◽  
Central United States

Abstract This study examines the evolution of soil moisture, evapotranspiration, vegetation, and atmospheric conditions during an unusual flash drought–flash recovery sequence that occurred across the south-central United States during 2015. This event was characterized by a period of rapid drought intensification (flash drought) during late summer that was terminated by heavy rainfall at the end of October that eliminated the extreme drought conditions over a 2-week period (flash recovery). A detailed analysis was performed using time series of environmental variables derived from meteorological, remote sensing, and land surface modeling datasets. Though the analysis revealed a similar progression of cascading effects in each region, characteristics of the flash drought such as its onset time, rate of intensification, and vegetation impacts differed between regions due to variations in the antecedent conditions and the atmospheric anomalies during its growth. Overall, flash drought signals initially appeared in the near-surface soil moisture, followed closely by reductions in evapotranspiration. Total column soil moisture deficits took longer to develop, especially in the western part of the region where heavy rainfall during the spring and early summer led to large moisture surpluses. Large differences were noted in how land surface models in the North American Land Data Assimilation System depicted soil moisture evolution during the flash drought; however, the models were more similar in their assessment of conditions during the flash recovery period. This study illustrates the need to use multiple datasets to track the evolution and impacts of rapidly evolving flash drought and flash recovery events.

scholarly journals SPATIO-TEMPORAL DISTRIBUTION OF WIND SPEED AND DAILY MAXIMUM WIND SPEED IN MOROCCO FOR THE PERIOD 2020-2050

2018 ◽  
pp. 68-71
Author(s):  
V. Khokhlov ◽  
Y. El Hadri
Keyword(s):  
Wind Speed ◽  
Climate Models ◽  
Regional Climate ◽  
Atlantic Coast ◽  
Surface Wind ◽  
Regional Climate Models ◽  
Maximum Wind Speed ◽  
Daily Maximum ◽  
Near Surface ◽  
Maximum Wind

The Moroccan energy system is highly dependent on external energy markets. Therefore, the current renewable energy strategy is focused on deployment of large-scale renewable technologies projects. Morocco has abundant wind resources. Estimations made by development organizations in Morocco quantify that the economic and technical potential of wind energy in Morocco amount to 26 GW. The aim of this study is to determine the possible quantitative indicators of wind speed, the daily maximum wind speed and their space-time distribution in the period 2020-2050 on the territory of Morocco. In study used data from regional climate modelling with a high spatial resolution of the project CORDEX. Simulations of regional climate models provide opportunities for a better understanding of atmospheric processes in the region and their possible future change. In the study use of regional climate models simulations for the RCP 4.5 scenario for the Africa region, presented in a rectangular coordinate system with a spatial resolution of ≈ 44 km. As a result of the regional climate models calculation, the mean monthly Near-Surface Wind Speed, and Daily Maximum Near-Surface Wind Speed values for the period 2020-2050 for the territory of Morocco were obtained. Regional climate models simulations showed that in Morocco will be dominated by gentle and moderate winds. The smallest values of the average wind speed are predicted in Fez − Meknes and Beni-Mellal − Henifra regions and will be about 3 m/s, the highest values can reach 9 m/s on the Atlantic coast to the south of Dakhla village. An analysis showed that in the future a character of annual course, in general, will have two types: in central mountain regions of Atlas, in the northeastern part of country and on the Mediterranean coast maximum wind speed will be register in winter; summer seasonal maximum of wind speed will be typical on the flat areas of the Atlantic coast, in the southern part of the country and on areas located behind the ridges of the Atlas mountains on the border with Algeria. The most favorable for the development of wind energy will be areas located on the shore of the Mediterranean Sea and the Atlantic Ocean and in the southern part of Morocco.

Impacts of Coastal Terrain on Warm-Sector Heavy-Rain-Producing MCSs in Southern China

2021 ◽  
Keyword(s):  
Heavy Rainfall ◽  
Southern China ◽  
Coastal Region ◽  
Vertical Wind Shear ◽  
Heavy Rain ◽  
Early Morning ◽  
Cold Pool ◽  
Near Surface ◽  
Warm Sector ◽  
Shear Component

Abstract Warm-sector heavy rainfall in southern China refers to the heavy rainfall that occurs within a weakly-forced synoptic environment under the influence of monsoonal airflows. It is usually located near the southern coast, and is characterized by poor predictability and a close relationship with coastal terrain. This study investigates the impacts of coastal terrain on the initiation, organization and heavy-rainfall potential of MCSs in warm-sector heavy rainfall over southern China using quasi-idealized WRF simulations and terrain-modification experiments. Typical warm-sector heavy rainfall events were selected to produce composite environments that forced the simulations. MCSs in these events all initiated in the early morning and developed into quasi-linear convective systems along the coast with a prominent backbuilding process. When the small coastal terrain is removed, the maximum 12-h rainfall accumulation decreases by ~46%. The convection initiation is advanced ~2 h with the help of orographic lifting associated with flow interaction with the coastal hills in the control experiment. Moreover, the coastal terrain weakens near-surface winds and thus decreases the deep-layer vertical wind shear component perpendicular to the coast and increases the component parallel to the coast; the coastal terrain also concentrates the moisture and instability over the coastal region by weakening the boundary layer jet. These modifications lead to faster upscale growth of convection and eventually a well-organized MCS. The coastal terrain is beneficial for backbuilding convection and thus persistent rainfall by providing orographic lifting for new cells on the western end of the MCS, and by facilitating a stronger and more stagnant cold pool, which stimulates new cells near its rear edge.

scholarly journals Modulation of Midtropospheric CO2 by the South Atlantic Walker Circulation*

2015 ◽  
Vol 72 (6) ◽  
pp. 2241-2247 ◽  
Author(s):  
Xun Jiang ◽  
Edward T. Olsen ◽  
Thomas S. Pagano ◽  
Hui Su ◽  
Yuk L. Yung
Keyword(s):  
South America ◽  
Atlantic Ocean ◽  
Large Scale ◽  
Climate Models ◽  
Walker Circulation ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
Strong Impact ◽  
The South ◽  
Near Surface

Abstract Midtropospheric CO2 data from the Atmospheric Infrared Sounder (AIRS) are used in this study to explore the variability of CO2 over the South Atlantic Ocean. It was found that the area-averaged CO2 over the South Atlantic Ocean is less than that over South America by about 1 ppm during December–March. This CO2 contrast is due to the large-scale vertical circulation over this region. During December–March, there is sinking motion over the South Atlantic Ocean. The sinking motion brings high-altitude air with a slightly lower concentration of CO2 to the midtroposphere. Meanwhile, air rising over South America brings near-surface air with a higher concentration of CO2 to the midtroposphere. As a result, the AIRS midtropospheric CO2 concentration is lower over the South Atlantic Ocean than over South America during December–March. The detrended AIRS midtropospheric CO2 difference correlates well with the inverted and detrended 400-hPa vertical pressure velocity difference between the South Atlantic and South America. Results obtained from this study demonstrate the strong impact of large-scale circulation on the vertical distribution of CO2 in the free troposphere and suggest that midtropospheric CO2 measurements can be used as an innovative observational constraint on the simulation of large-scale circulations in climate models.

Differing Responses of the Diurnal Cycle of Land Surface and Air Temperatures to Deforestation

2019 ◽  
Vol 32 (20) ◽  
pp. 7067-7079 ◽  
Author(s):  
Liang Chen ◽  
Paul A. Dirmeyer
Keyword(s):  
Land Cover ◽  
Diurnal Cycle ◽  
Land Surface ◽  
Climate Models ◽  
Surface Air Temperature ◽  
Daily Maximum ◽  
Near Surface ◽  
Diurnal Cycles ◽  
Air Temperatures ◽  
Temperature Responses

ABSTRACT Recent studies have shown the impacts of historical land-use land-cover changes (i.e., deforestation) on hot temperature extremes; contradictory temperature responses have been found between studies using observations and climate models. However, different characterizations of surface temperature are sometimes used in the assessments: land surface skin temperature Ts is more commonly used in observation-based studies while near-surface air temperature T2m is more often used in model-based studies. The inconsistent use of temperature variables is not inconsequential, and the relationship between deforestation and various temperature changes can be entangled, which complicates comparisons between observations and model simulations. In this study, the responses in the diurnal cycle of summertime Ts and T2m to deforestation are investigated using the Community Earth System Model. For the daily maximum, opposite responses are found in Ts and T2m. Due to decreased surface roughness after deforestation, the heat at the land surface cannot be efficiently dissipated into the air, leading to a warmer surface but cooler air. For the daily minimum, strong warming is found in T2m, which exceeds daytime cooling and leads to overall warming in daily mean temperatures. After comparing several climate models, we find that the models agree in daytime land surface (Ts) warming, but different turbulent transfer characteristics produce discrepancies in T2m. Our work highlights the need to investigate the diurnal cycles of temperature responses carefully in land-cover change studies. Furthermore, consistent consideration of temperature variables should be applied in future comparisons involving observations and climate models.

scholarly journals Geoengineering: Impact of Marine Cloud Brightening Control on the Extreme Temperature Change over East Asia

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1345
Author(s):  
Do-Hyun Kim ◽  
Ho-Jeong Shin ◽  
Il-Ung Chung
Keyword(s):  
East Asia ◽  
Radiative Forcing ◽  
Climate Models ◽  
Extreme Temperature ◽  
Global Climate Models ◽  
Maximum Temperature ◽  
Daily Minimum Temperature ◽  
Daily Maximum Temperature ◽  
Daily Maximum ◽  
Extreme Temperatures

We investigated the effect of artificial marine cloud brightening on extreme temperatures over East Asia. We used simulation data from five global climate models which have conducted the GeoMIP G4cdnc experiment. G4cdnc was designed to simulate an increase in the cloud droplet number concentration of the global marine lower clouds by 50% under the greenhouse gas forcing of the RCP4.5 scenario. G4cdnc decreased the net radiative forcing in the top of the atmosphere more over the ocean, alleviating the rise in mean temperature under RCP4.5 forcing. For extreme temperatures, G4cdnc reduced both the monthly minimum of daily minimum temperature (TNn) and monthly maximum of daily maximum temperature (TXx). The response of TNn was higher than that of TXx, especially in the winter, over the Sea of Okhotsk and the interior of the continent. This spatial heterogeneity and seasonality of the response were associated with sea ice–albedo and snow–albedo feedbacks. We also calculated the efficacy of warming mitigation as a measure of the relative effect of geoengineering. The efficacy for TXx was higher than that for TNn, opposite to the absolute effect. After the termination of geoengineering, both TNn and TXx tended to rapidly revert to their trend under the RCP4.5 forcing.

Climate change and associated fire potential for the south-eastern United States in the 21st century

2013 ◽  
Vol 22 (8) ◽  
pp. 1034 ◽  
Author(s):  
Anthony P. Bedel ◽  
Thomas L. Mote ◽  
Scott L. Goodrick
Keyword(s):  
21St Century ◽  
Climate Models ◽  
Convective Precipitation ◽  
Drought Indices ◽  
Deep South ◽  
Eastern United States ◽  
The South ◽  
Near Surface ◽  
South Eastern ◽  
Southern Half

Climate models indicate that the climate of the south-eastern US will experience increasing temperatures and associated evapotranspiration in the 21st century. The current study found that conditions in the south-eastern US will likely become drier overall, given a warmer environment during future winter and spring seasons. This study examined the potential effects of a warmer climate in the 21st century on relevant meteorological fire parameters (e.g. total and convective precipitation, 500-hPa geopotential heights, near-surface relative humidity) and popular fire indices (e.g. Haines and Keetch–Byram Drought Indices) in the south-eastern US. Although the results offered conflicting implications in portions of the study domain, the southern half of the south-eastern US (including the Deep South, the southern Piedmont and Florida) exhibited the highest potential for increasing fire activity in the mid-21st century, given maximum warming and drying in these areas, especially in the spring season.

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