scholarly journals Atlantic hurricane response to Saharan greening and reduced dust emissions during the mid-Holocene

2021 ◽  
Vol 17 (2) ◽  
pp. 675-701
Author(s):  
Samuel Dandoy ◽  
Francesco S. R. Pausata ◽  
Suzana J. Camargo ◽  
René Laprise ◽  
Katja Winger ◽  
...  
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Boreal Summer ◽  
Orbital Forcing ◽  
African Easterly Waves ◽  
Solar Insolation ◽  
Airborne Dust ◽  
Dust Emissions ◽  
Easterly Waves ◽  
Hurricane Season

Abstract. We use a high-resolution regional climate model to investigate the changes in Atlantic tropical cyclone (TC) activity during the period of the mid-Holocene (MH: 6000 years BP) with a larger amplitude of the seasonal cycle relative to today. This period was characterized by increased boreal summer insolation over the Northern Hemisphere, a vegetated Sahara and reduced airborne dust concentrations. A set of sensitivity experiments was conducted in which solar insolation, vegetation and dust concentrations were changed in turn to disentangle their impacts on TC activity in the Atlantic Ocean. Results show that the greening of the Sahara and reduced dust loadings (MHGS+RD) lead to a larger increase in the number of Atlantic TCs (27 %) relative to the pre-industrial (PI) climate than the orbital forcing alone (MHPMIP; 9 %). The TC seasonality is also highly modified in the MH climate, showing a decrease in TC activity during the beginning of the hurricane season (June to August), with a shift of its maximum towards October and November in the MHGS+RD experiment relative to PI. MH experiments simulate stronger hurricanes compared to PI, similar to future projections. Moreover, they suggest longer-lasting cyclones relative to PI. Our results also show that changes in the African easterly waves are not relevant in altering the frequency and intensity of TCs, but they may shift the location of their genesis. This work highlights the importance of considering vegetation and dust changes over the Sahara region when investigating TC activity under a different climate state.

scholarly journals Atlantic Hurricane response to Sahara greening and reduced dust emissions during the mid-Holocene

2020 ◽  
Author(s):  
Samuel Dandoy ◽  
Francesco S.R. Pausata ◽  
Suzana J. Camargo ◽  
René Laprise ◽  
Katja Winger ◽  
...  
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Boreal Summer ◽  
Orbital Forcing ◽  
African Easterly Waves ◽  
Warm Climate ◽  
Solar Insolation ◽  
Airborne Dust ◽  
Easterly Waves ◽  
Hurricane Season

Abstract. We use a high-resolution regional climate model to investigate the changes in Atlantic tropical cyclone (TC) activity during a warm climate state, the mid-Holocene (MH: 6,000 yrs BP). This period was characterized by increased boreal summer insolation, a vegetated Sahara, and reduced airborne dust concentrations. A set of sensitivity experiments were conducted in which solar insolation, vegetation and dust concentrations were changed in turn to disentangle their impacts on TC activity. Results show that the greening of the Sahara and reduced dust loadings (MHGS+RD) lead to a larger increase in the number of Atlantic TCs (27 %) relative to the pre-industrial climate (PI) than the orbital forcing alone (MHPMIP; 9 %). The TC seasonality is also highly modified in the MH climate, showing a decrease in TC activity during the beginning of the hurricane season (June to August), with a shift of its maximum towards October and November in the MHGS+RD experiment relative to PI. MH experiments simulate stronger hurricanes compared to PI, similar to future projections. Moreover, they suggest longer lasting cyclones relative to PI. Our results also show that changes in the African Easterly Waves are not relevant in altering the frequency and intensity of TCs, but they may shift the location of their genesis. This work highlights the importance of considering vegetation and dust changes over the Sahara region when investigating TC activity under a different climate state.

Simulations of the West African Monsoon with a Superparameterized Climate Model. Part II: African Easterly Waves

2014 ◽  
Vol 27 (22) ◽  
pp. 8323-8341 ◽  
Author(s):  
Rachel R. McCrary ◽  
David A. Randall ◽  
Cristiana Stan
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Deep Convection ◽  
West African Monsoon ◽  
General Circulation Models ◽  
African Easterly Waves ◽  
Climate System Model ◽  
Easterly Waves ◽  
Cloud Resolving Model ◽  
The Waves

Abstract The relationship between African easterly waves and convection is examined in two coupled general circulation models: the Community Climate System Model (CCSM) and the “superparameterized” CCSM (SP-CCSM). In the CCSM, the easterly waves are much weaker than observed. In the SP-CCSM, a two-dimensional cloud-resolving model replaces the conventional cloud parameterizations of CCSM. Results show that this allows for the simulation of easterly waves with realistic horizontal and vertical structures, although the model exaggerates the intensity of easterly wave activity over West Africa. The simulated waves of SP-CCSM are generated in East Africa and propagate westward at similar (although slightly slower) phase speeds to observations. The vertical structure of the waves resembles the first baroclinic mode. The coupling of the waves with convection is realistic. Evidence is provided herein that the diabatic heating associated with deep convection provides energy to the waves simulated in SP-CCSM. In contrast, horizontal and vertical structures of the weak waves in CCSM are unrealistic, and the simulated convection is decoupled from the circulation.

scholarly journals Future Climate in the Tibetan Plateau from a Statistical Regional Climate Model

2013 ◽  
Vol 26 (24) ◽  
pp. 10125-10138 ◽  
Author(s):  
Xiuhua Zhu ◽  
Weiqiang Wang ◽  
Klaus Fraedrich
Keyword(s):  
Tibetan Plateau ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Early Summer ◽  
Maximum Temperature ◽  
Boreal Summer ◽  
The Tibetan Plateau ◽  
Temperature Trends ◽  
Precipitation Increase

Abstract The authors use a statistical regional climate model [Statistical Regional Model (STAR)] to project the Tibetan Plateau (TP) climate for the period 2015–50. Reanalysis datasets covering 1958–2001 are used as a substitute of observations and resampled by STAR to optimally fit prescribed linear temperature trends derived from the Max Planck Institute Earth System Model (MPI-ESM) simulations for phase 5 of the Coupled Model Intercomparison Project (CMIP5) under the representative concentration pathway 2.6 (RCP2.6) and RCP4.5 scenarios. To assess the related uncertainty, temperature trends from carefully selected best/worst ensemble members are considered. In addition, an extra projection is forced by observed temperature trends in 1958–2001. The following results are obtained: (i) Spatial average temperature will increase by 0.6°–0.9°C; the increase exceeds 1°C in all months except in boreal summer, thus indicating a reduced annual cycle; and daily minimum temperature rises faster than daily maximum temperature, resulting in a narrowing of the diurnal range of near-surface temperature. (ii) Precipitation increase mainly occurs in early summer and autumn possibly because of an earlier onset and later withdrawal of the Asian summer monsoon. (iii) Both frost and ice days decrease by 1–2 days in spring, early summer, and autumn, and the decrease of frost days on the annual course is inversely related to the precipitation increase. (iv) Degree-days increase all over the TP with peak amplitude in the Qaidam Basin and the southern TP periphery, which will result in distinct melting of the local seasonal frozen ground, and the annual temperature range will decrease with stronger amplitude in south TP.

Predicting land susceptibility to atmospheric dust emissions in central Iran by combining integrated data mining and a regional climate model

2021 ◽  
Vol 12 (4) ◽  
pp. 172-187
Author(s):  
Hamid Gholami ◽  
Aliakbar Mohamadifar ◽  
Setareh Rahimi ◽  
Dimitris G. Kaskaoutis ◽  
Adrian L. Collins
Keyword(s):  
Data Mining ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Central Iran ◽  
Atmospheric Dust ◽  
Dust Emissions

scholarly journals Potential Dust Induced Changes on the Seasonal Variability of Temperature Extremes Over the Sahel: A Regional Climate Modeling Study

2021 ◽  
Vol 8 ◽  
Author(s):  
Ibrahima Diba ◽  
Jules Basse ◽  
Mamadou Ndiaye ◽  
Hamady Ngansou Sabaly ◽  
Arona Diedhiou ◽  
...  
Keyword(s):  
Energy Demand ◽  
Climate Model ◽  
Mineral Dust ◽  
Climate Modeling ◽  
Regional Climate ◽  
Heat Index ◽  
Dust Particles ◽  
Temperature Extremes ◽  
Dust Emissions ◽  
The Impact

The aim of this study is to simulate the impact of mineral dust emissions from the Sahel–Saharan zone on temperature extremes over the Sahel. To achieve this goal, we performed two numerical simulations: one with the standard version of the regional climate model RegCM4 (no dust run) and another one with the same version of this model incorporating a dust module (dust run). The difference between both versions of the model allowed to isolate the impacts of mineral dust emissions on temperature extremes. The results show that the accumulation of mineral dust into the atmosphere leads to a decrease of the frequency of warm days, very warm days, and warm nights over the Sahel. This decrease is higher during the MAM (March-April-May) and JJA (June-July-August) periods especially in the northern and western parts of the Sahel. The impact of the mineral dust emissions is also manifested by a decrease of the frequency of tropical nights especially during MAM in the northern Sahel. When considering the warm spells, mineral particles tend to weaken them especially in MAM and JJA in the northern Sahel. To estimate the potential impacts of the mineral dust accumulation on heat stress, the heat index and the humidex are used. The analysis of the heat index shows that the dust impact is to reduce the health risks particularly in the northern Sahel during the MAM period, in the western Sahel during JJA, and in the southern and the northeastern parts of the Sahel during the SON (September-October-November) period. As for the humidex, it is characterized by a decrease especially in the northern Sahel for all seasons. This reduction of the occurrence of thermal extremes may have a positive effect on the energy demand for cooling and on global health. However, the accumulation of dust particles in the atmosphere may also increase the meningitis incidence and prevalence.

scholarly journals A GCM comparison of Pleistocene super-interglacial periods in relation to Lake El'gygytgyn, NE Arctic Russia

2015 ◽  
Vol 11 (7) ◽  
pp. 979-989 ◽  
Author(s):  
A. J. Coletti ◽  
R. M. DeConto ◽  
J. Brigham-Grette ◽  
M. Melles
Keyword(s):  
Land Surface ◽  
Forest Cover ◽  
Climate Model ◽  
Regional Climate ◽  
The Arctic ◽  
Boreal Summer ◽  
Climate Data ◽  
Lake El’Gygytgyn ◽  
Proxy Reconstructions ◽  
Temperature Proxy

Abstract. Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stages (MISs) 1 (9 ka), 5e (127 ka), 11c (409 ka) and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the mean temperature of the warmest month (MTWM) indicate conditions up to 0.4, 2.1, 0.5 and 3.1 °C warmer than today during MIS 1, 5e, 11c and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer (JJA) orbital forcing, the extraordinary warmth of MIS 11c compared to the other interglacials in the Lake El'gygytgyn temperature proxy reconstructions remains difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice and circum-Arctic land ice feedbacks on the modeled climate of the Beringian interior. Simulations accounting for climate–vegetation–land-surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on northeast Asian temperature during the warmth of stages 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic Ocean does have some effect on Lake El'gygytgyn's regional climate, but the exceptional warmth of MIS l1c remains enigmatic compared to the modest orbital and greenhouse gas forcing during that interglacial.

scholarly journals On the Influence of Vegetation Cover Changes and Vegetation-Runoff Systems on the Simulated Summer Potential Evapotranspiration of Tropical Africa Using RegCM4

2021 ◽  
Author(s):  
Samy A. Anwar ◽  
Ossénatou Mamadou ◽  
Ismaila Diallo ◽  
Mouhamadou Bamba Sylla
Keyword(s):  
Soil Moisture ◽  
Vegetation Cover ◽  
Climate Model ◽  
Potential Evapotranspiration ◽  
Regional Climate ◽  
Boreal Summer ◽  
Climatic Research Unit ◽  
Tropical Africa ◽  
Infiltration Capacity ◽  
Community Land Model

AbstractThe community land model version 4.5 provides two ways for treating the vegetation cover changes (a static versus an interactive) and two runoff schemes for tracking the soil moisture changes. In this study, we examined the sensitivity of the simulated boreal summer potential evapotranspiration (PET) to the aforementioned options using a regional climate model. Three different experiments with each one covering 16 years have been performed. The two runoff schemes were designated as SIMTOP (TOP) and variable infiltration capacity (VIC). Both runoff schemes were coupled to the carbon–nitrogen (CN) module, thus the vegetation status can be influenced by soil moisture changes. Results show that vegetation cover changes alone affect considerably the simulated 2-m mean air temperature (T2M). However, they do not affect the global incident solar radiation (RSDS) and PET. Conversely to the vegetation cover changes alone, the vegetation-runoff systems affect both the T2M and RSDS. Therefore, they considerably affect the simulated PET. Also, the CN-VIC overestimates the PET more than the CN-TOP compared to the Climatic Research Unit observational dataset. In comparison with the static vegetation case and CN-VIC, the CN-TOP shows the least bias of the simulated PET. Overall, our results show that the vegetation-runoff system is relevant in constraining the PET, though the CN-TOP can be recommended for future studies concerning the PET of tropical Africa.

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