Assessing the Performance of CMIP6 Models in Simulating Droughts across Global Drylands

Both the attribution of historical change and future projections of droughts rely heavily on climate modeling. However,reasonable drought simulations have remained a challenge, and the related performances of the current state-of-the-art Coupled Model Intercomparison Project phase 6(CMIP6) models remain unknown. Here, both the strengths and weaknesses of CMIP6 models in simulating droughts and corresponding hydrothermal conditions in drylands are assessed.While the general patterns of simulated meteorological elements in drylands resemble the observations, the annual precipitation is overestimated by ~33%(with a model spread of 2.3%–77.2%), along with an underestimation of potential evapotranspiration(PET) by ~32%(17.5%–47.2%). The water deficit condition, measured by the difference between precipitation and PET, is 50%(29.1%–71.7%) weaker than observations. The CMIP6 models show weaknesses in capturing the climate mean drought characteristics in drylands, particularly with the occurrence and duration largely underestimated in the hyperarid Afro-Asian areas. Nonetheless, the drought-associated meteorological anomalies, including reduced precipitation, warmer temperatures, higher evaporative demand, and increased water deficit conditions, are reasonably reproduced. The simulated magnitude of precipitation(water deficit) associated with dryland droughts is overestimated by 28%(24%) compared to observations. The observed increasing trends in drought fractional area,occurrence, and corresponding meteorological anomalies during 1980–2014 are reasonably reproduced. Still, the increase in drought characteristics, associated precipitation and water deficit are obviously underestimated after the late 1990s,especially for mild and moderate droughts, indicative of a weaker response of dryland drought changes to global warming in CMIP6 models. Our results suggest that it is imperative to employ bias correction approaches in drought-related studies over drylands by using CMIP6 outputs.

Understanding and Attribution of Extreme Heat and Drought Events in 2022: Current Situation and Future Challenges

Extreme weather events and their consequential impacts have been a key feature of the climate in recent years in many parts of the world,with many partly attributed to ongoing global-scale warming.The past year,2022,has been no exception,with further records being broken.The year was marked by unprecedented heatwaves and droughts with highly unusual spatial extent,duration and intensity,with one measure indicating an aggregated and overall intensity of extreme heat events worldwide not seen since at least 1950.The extreme drought measured by surface soil moisture covered 47.3%of global land areas in 2022,which was the second most widespread year since 1980.Here,we examine notable events of the year in five major regions of the world:China’s Yangtze River region,western Europe,the western U.S.,the Horn of Africa and central South America.For each event,we review the potential roles of circulation,oceanic forcing(especially the“triple-dip”La Niña)and anthropogenic climate change,with an aim of understanding the extreme events in 2022 from a global perspective.This will serve as a reference for mechanism understanding,prediction and attribution of extreme events.

Evolution of Meteorological Conditions during a Heavy Air Pollution Event under the Influence of Shallow Foehn in Urumqi, China

The air pollution in Urumqi which is located on the northern slope of the Tianshan Mountains in northwestern China,is very serious in winter.Of particular importance is the influence of terrain-induced shallow foehn,known locally as elevated southeasterly gale(ESEG).It usually modulates atmospheric boundary layer structure and wind field patterns and produces favorable meteorological conditions conducive to hazardous air pollution.During 2013-17,Urumqi had an average of 50 d yr-1 of heavy pollution(daily average PM2.5 concentration>150μg m-3),of which 41 days were in winter.The majority(71.4%)of heavy pollution processes were associated with the shallow foehn.Based on microwave radiometer,wind profiler,and surface observations,the surface meteorological fields and boundary layer evolution during the worst pollution episode in Urumqi during 16-23 February 2013 are investigated.The results illustrate the significant role of shallow foehn in the building,strengthening,and collapsing of temperature inversions.There were four wind field patterns corresponding to four different phases during the whole pollution event.The most serious pollution phase featured shallow foehn activity in the south of Urumqi city and the appearance of an intense inversion layer below 600 m.Intense convergence caused by foehn and mountain-valley winds was sustained during most of the phase,resulting in pollutants sinking downward to the lower boundary layer and accumulating around urban area.The key indicators of such events identified in this study are highly correlated to particulate matter concentrations and could be used to predict heavy pollution episodes in the feature.

Application of Capture and Recapture Method for Estimating the Population Size of Men Who Have Sex with Men in Chiang Mai, Thailand

Background: Men who have sex with men (MSM) are highly vulnerable to HIV infection, but this population can be particularly difficult to reach in Thailand. This study aimed to estimate the number of MSM in Chiang Mai Thailand, in order to plan HIV control and prevention. Methods: The total of 348 potential MSM were identified at eight contact locations, including two public parks, two bars, two massage parlors and two pubs in Chiang Mai. Trained 16 research enumerators and 16 enumerators were trained to extend a recruitment of brooches to MSM. The MSMs were captured one week apart. A record was kept of when, where and by whom the invitation was extended and received, and of refusals. The total estimate of MSM was derived from capture-recapture calculation. Results: The total MSM in Chiang Mai Thailand estimated by capture and recapture method was 733 (95%CI = 480 - 948) or the estimate was 7.3% (95%CI = 7.1% - 14.1%). Conclusions: Capture and recapture method can be used to enumerate and provide accurate and reliable estimates of the MSM population in any area, provided that certain conditions are controlled. MSM who are engaged in personal community represent a sizeable population who urgently need to be targeted by HIV and STDs prevention strategies.

Risk Factors Affecting Condom Use among Royal Thai Army Conscripts in Thailand

The study was conducted to explore factors associated with condom use of young Thai men conscripts. Methods: A cross-sectional study was conducted. Participants were 159 conscripts in second year who served in the Royal Thai Army by lottery method. Demographic data, sexual history including condom use, HIV and STDs and knowledge were collected using a self-administered questionnaire. Logistic regression was used to analyze the data. Results: Condom use at the last sex was 41.18% of the conscripts aged 20 - 27 years and secondary school education completed of 74.2%. 25.78% had experience with drugs used but injection was rare (6.9%). Age at the first sex was reported lowest at 11 years, 9.4% reported first sex with men and 21.38% were married. The participants have sexual history (last six months) with female only of 83.2%, male only of 4.1% and both of 14.6%. Among these only 12.6% reported every time of condom use and 19.5% never used condom. Older age, higher education, drinking alcohol, drugs use and higher knowledge were associated with condom use with statistical significance. Conclusions: Condom use among male Thai conscripts was low. Education and a condom use program are urgently needed to prevent future spread of HIV and STDs.

Long-term changes in the effect of drought stress on ecosystems across global drylands

Droughts are one of the climate extremes that occur frequently in drylands,constraining the terrestrial carbon uptake and water cycle processes.Studies about the long-term changes in the effect of drought stress on dryland ecosystems under global warming are still insufficient so far.Here we comprehensively investigate long-term changes in droughts and the effect of drought stresses on ecosystems across global drylands for 1982–2015,and further reveal changes in the configurations of the key meteorological and ecological factors of droughts,by using observation and reanalysis datasets.Climatically,the spatial patterns of intensity,occurrence,duration and severity of all drought categories across global drylands are highly consistent with each other.Associated with severe droughts,drylands witness insufficient precipitation(-12.4 mm mon^(-1)area-averaged over global drylands),warmer temperature(0.6℃),water deficit(-19.0 mm mon^(-1)),higher atmospheric aridity(0.06 k Pa),lower soil moisture(-0.03 m^(3)m^(-3)),suppressed vegetation growth and declined carbon uptake(-0.13 g C m^(-2)d^(-1)).The affected area,occurrence,duration and severity for mild to severe droughts in drylands and the anomalies of meteorological and ecological factors for all drought categories have increased significantly during 1982-2015.Specifically,when droughts occur,the precipitation deficit is weakened at a rate of 3.7–9.6 mm mon^(-1)(30 yr)^(-1),the higher temperature(atmospheric aridity)is further intensified at 0.71–0.87-1(30 yr)^(-1)(39–47 Pa(30 yr)^(-1)),the water(soil moisture)deficit is relieved at 1.7–5.1 mm mon^(-1)(30yr)^(-1)(4.1×10^(-3)–7.4×10^(-3)m^(3)m^(-3)(30 yr)^(-1)),and the suppressed vegetation growth is generally alleviated at 0.98×10^(-2)–1.2×10^(-2)(30 yr)^(-1).Since the 2000s,the increasing trend in the suppressed vegetation growth during droughts tends to stagnate over about 50%of the dryland area.By checking the probability density function,the configurations of the key meteorological and ecological factors of droughts show significant differences between the periods before and after 2000.The probability of drought stress caused by precipitation and soil moisture deficit has decreased by 20%and 10%,respectively,while that caused by higher temperature and atmospheric aridity has been doubled,and increased by 26%and 15%,respectively.Thus,the impact of drought stress on dryland ecosystems caused by atmospheric aridity are increasing under global warming.

Mechanism insight into the enhanced photocatalytic purification of antibiotic through encapsulated architectures coupling of crystalline Cu_(2)O/amorphous TiFe layer double hydroxide

Amorphous materials are one of the important candidates for improving heterogeneous photocata-lysts because of their unique electronic structures and abundant catalytic sites originating from dis-order atomic arrangements.However,there is still much room for the development of new crys-talline/amorphous heterogeneous composites for photocatalytic application.Hence efficient synthetic strategies for preparing new crystalline/amorphous heterojunctions are highly desired.Herein,we have realized the deep optimization of photocatalytic activity by fabricating crystalline/amorphous Cu_(2)O/Ti-Fe layer double hydroxide(LDH)heterojunctions.Thanks to the typical Z-scheme mechanism originating from the crystalline/amorphous interfaces,the photocharge separation and catalytic active sites obviously enhance compared to single Cu_(2)O and LDH counterparts.As expected,the photocatalytic removal of tetra-cycline(TC)of the as-prepared Cu_(2)O/Ti-Fe LDH was over 5.2 and 2.2 times those of the pristine Cu_(2)O nanospheres and Ti-Fe LDH nanosheets.This work illustrates the origin of crystalline Cu_(2)O nanospheres encapsulated in amorphous Ti-Fe layer double hydroxide nanosheets for enhanced photocatalytic activity driven by visible light,and provide a general Cu_(2)O-templated solution-phase synthetic method for the synthesis of novel double-metal layer double hydroxide amorphous nanostructures.

The Asian Subtropical Westerly Jet Stream in CRA-40, ERA5, and CFSR Reanalysis Data:Comparative Assessment

The Asian subtropical westerly jet(AWJ) exerts crucial influences on Eurasian continent weather and climate. This paper analyzes the advantages and limitations of CRA-40, which is China's first generation 40-yr(1979–2018) global atmosphere and land reanalysis product, in describing the characteristics of AWJ, compared with the ECMWF Reanalysis version 5(ERA5) and NCEP Climate Forecast System Reanalysis(CFSR). The results show a close agreement across the three reanalyses on the whole.(1) In terms of climatology, overall differences of 200-h Pa zonal wind across the three reanalyses are within ± 0.5 m s^(-1)(i.e., ± 2%). Large differences with maxima of ± 2 m s^(-1)(±5%) appear over the Iranian Plateau and south of the Tibetan Plateau in the mid–upper troposphere in winter.(2) For seasonal cycle, the position and intensity of the AWJ centers in the three reanalyses are highly consistent, with correlation coefficient over 0.98. But there are some discrepancies in the zonal shift of the western AWJ center during the transition season.(3) On the interannual timescale, intensity of all AWJ centers varies consistently among the three reanalyses, while larger differences appear in their meridional displacement, especially in the eastern AWJ center.(4)For long-term variations, the three reanalyses all present a significant northward movement of the westerly jet axis in winter, and a southward displacement over central Asia(40°–80°E) and a northward migration over East Asia(80°–110°E) in summer. Thus, this study has provided confidence that CRA-40 has comparable performance with ERA5 and CFSR in depicting the characteristics of AWJ.

Boosting photocatalytic hydrogen evolution of g-C_(3)N_(4) catalyst via lowering the Fermi level of co-catalyst

The photocatalytic performances are highly dependent on the charge separation and surface reaction kinetics of photocatalysts.Aiming at figuring out the effects of co-catalyst with the lower Fermi level on photocatalytic activity,we tuned the Fermi level of Pt nanoparticles on g-C_(3)N_(4)(GCN)by introducing Co atom.Experimental results show that lowering the Fermi level of co-catalyst does not alter light absorption of GCN due to the invariable structure.Besides,Pt_(3)Co with a lower Fermi level contributes less positive influence on charge separation in GCN due to an opposite effect from the stronger electron-trap ability of Pt_(3)Co and increased band bending in GCN-Pt_(3)Co.The density functional theory(DFT)calculations indicate that GCN-Pt_(3)Co has faster surface reaction kinetics than GCN-Pt,owing to easier dissociation of H_(2)O molecules and faster desorption of H^(*)on Pt_(3)Co.Consequently,GCN-Pt_(3)Co exhibits an excellent H_(2) evolution rate with 2.91 mmol g^(-1)·h^(-1),which 2.67 times that of GCN-Pt.

TRAVELING WAVES FOR A SIRS MODEL WITH NONLOCAL DIFFUSION

In this paper, we study a delayed SIRS model with nonlocal diffusion. The well posedness of the model is investigated. Furthermore, we concern with the problem of traveling wave solutions. By using the partial quasi-monotone condition, cross-iteration scheme and fixed-point theorem, sufficient conditions are derived for the existence of traveling waves connecting the two equilibria which depends on the existence of a pair of upper solution and lower solution. We in fact construct a pair of upper solution and lower solution concretely to guarantee the existence of traveling waves.