ALBERT

Description: Ce 3+ , Nd 3+ codoped (Sr 0.6 Ca 0.4 ) 3 (Al 0.6 Si 0.4 )O 4.4 F 0.6 phosphors were synthesized through the high-temperature solid-state reaction method. Luminescence spectra, absorption spectra, and decay lifetimes of these samples have been measured to prove the energy-transfer process from Ce 3+ to Nd 3+ . Under UV and blue light excitation, (Sr 0.6 Ca 0.4 ) 3 (Al 0.6 Si 0.4 )O 4.4 F 0.6 :Ce 3+ ,Nd 3+ phosphors exhibit near-infrared (NIR) emission, mainly peaking at 1093 nm and secondarily at 916 nm. The NIR emission matches well with the band gap of c-Si. Results of this work suggest that the (Sr 0.6 Ca 0.4 ) 3 (Al 0.6 Si 0.4 )O 4.4 F 0.6 :Ce 3+ , Nd 3+ phosphors have potential application as down-shifting luminescent convertor for enhancing the photoelectric conversion efficiency of c-Si solar cell.

Description: The geographical shift of global anthropogenic aerosols from the developed countries to the Asian continent since the 1980s could potentially perturb the regional and global climate due to aerosol-cloud-radiation interactions. We use an atmospheric general circulation model with different aerosol scenarios to investigate the radiative and microphysical effects of anthropogenic aerosols from different regions on the radiation budget, precipitation, and large-scale circulations. An experiment contrasting anthropogenic aerosol scenarios in 1970 and 2010 shows that the altered cloud reflectivity and solar extinction by aerosols results in regional surface temperature cooling in East and South Asia, and warming in US and Europe respectively. These aerosol induced temperature changes are consistent with the relative temperature trends from 1980 to 2010 over different regions in the reanalysis data. A reduced meridional streamfunction and zonal winds over the tropics as well as a poleward shift of the jet stream suggest weakened and expanded tropical circulations, which are induced by the redistributed aerosols through a relaxing of the meridional temperature gradient. Consequently, precipitation is suppressed in the deep tropics and enhanced in the sub-tropics. Our assessments of the aerosol effects over the different regions suggest that the increasing of Asian pollution accounts for the weakening of the tropics circulation, while the decreasing of pollution in Europe and US tends to shift the circulation systems southward. Moreover, the aerosol indirect forcing is predominant over the total aerosol forcing in magnitude, while aerosol radiative and microphysical effects jointly shape the meridional energy distributions and modulate the circulation systems.

Description: Nitrogen (N) serves as an important mineral element affecting plant productivity and nutritional quality. However, few studies have addressed the interactive effects of elevated CO 2 and precipitation change on leaf N of dominant grassland genera such as Stipa L. This has restricted our understanding of the responses of grassland to climate change. We simulated the interactive effects of elevated CO 2 concentration and varied precipitation on leaf N concentration (N mass ) of four Stipa species ( Stipa baicalensis , Stipa bungeana , Stipa grandis, and Stipa breviflora ; the most dominant species in arid and semiarid grassland) using open-top chambers (OTCs). The relationship between the N mass of these four Stipa species and precipitation well fits a logarithmic function. The sensitivity of these four species to precipitation change was ranked as follows: S. bungeana  〉  S. breviflora  〉  S. baicalensis  〉  S. grandis . The N mass of S. bungeana was the most sensitive to precipitation change, while S. grandis was the least sensitive among these Stipa species. Elevated CO 2 exacerbated the effect of precipitation on N mass . N mass decreased under elevated CO 2 due to growth dilution and a direct negative effect on N assimilation. Elevated CO 2 reduced N mass only in a certain precipitation range for S. baicalensis (163–343 mm), S. bungeana (164–355 mm), S. grandis (148–286 mm), and S. breviflora (130–316 mm); severe drought or excessive rainfall would be expected to result in a reduced impact of elevated CO 2 . Elevated CO 2 affected the N mass of S. grandis only in a narrow precipitation range. The effect of elevated CO 2 reached a maximum when the amount of precipitation was 253, 260, 217, and 222 mm for S. baicalensis , S. bungeana , S. grandis, and S. breviflora , respectively. The N mass of S. grandis was the least sensitive to elevated CO 2 . The N mass of S. breviflora was more sensitive to elevated CO 2 under a drought condition compared with the other Stipa species. Elevated CO 2 decreased N mass that caused by the combination of growth dilution and assimilation inhibition. The effect of elevated CO 2 was influenced by precipitation. The relationship between N mass and precipitation could be better observed with by a logarithmic function for the four Stipa species. The N mass of S.grandis was the least sensitive among these four species. Under drought condition, the effect of elevated CO 2 on S. breviflora was more obvious than the other three species.

Description: We study the relationships between aerosols, clouds, and large scale dynamics over a north coastal Australia (NCA) region and a southeast Australia (SEA) region during the period 2002–2009 to evaluate the applicability of the aerosol microphysics-radiation-effect (MRE) theory proposed by Koren et al. (2008) in a low aerosol environment. We use aerosol optical depth (τa), fire counts, and cloud fraction (fc) from Aqua-MODIS, and NCEP Reanalysis vertical velocities at 500 mb (ω500) as a proxy for dynamic regime. In the NCA we find a monotonic increase fc (35%, absolute fc) as a function of increasing τa. In the SEA, we find that fc initially increases by 25% with increasing τa, followed by a slow systematic decrease (∼18%) with higher τa. We show that the MRE theory proposed by Koren et al. (2008) adequately represents the variation of fc with τa in both the NCA and SEA. By conditionally sorting data by ω500 we investigate the role dynamics plays in controlling the τa-fc relationship and the rate at which fc changes with τa. We find that the MRE theory can be used to empirically fit both −ω500 and +ω500 observations. By analyzing meteorological parameters from the NCEP Reanalysis, we find that variations in local meteorology are not likely the cause of the observed relationships of τa and fc during biomass burning seasons. However, additional factors such as aerosol type and cloud type may play a role.

Description: The large spread of model equilibrium climate sensitivity (ECS) is mainly caused by the differences in the simulated marine boundary layer cloud (MBLC) radiative feedback. We examine the variations of MBLC fraction in response to the changes of sea surface temperature (SST) at seasonal and centennial timescales for 27 climate models that participated in the Coupled Model Intercomparison Project Phase 3 and Phase 5. We find that the inter-model spread in the seasonal variation of MBLC fraction with SST is strongly correlated with the inter-model spread in the centennial MBLC fraction change per degree of SST warming and that both are well correlated with ECS. Seven models that are consistent with the observed seasonal variation of MBLC fraction with SST at a rate −1.28±0.56 %/K all have ECS higher than the multi-model mean of 3.3 K yielding an ensemble-mean ECS of 3.9 K and a standard deviation of 0.45 K.

Description: Using NASA's A-Train satellite measurements, we evaluate the accuracy of cloud water content (CWC) and water vapor mixing ratio (H2O) outputs from 19 climate models submitted to the Phase 5 of Coupled Model Intercomparison Project (CMIP5), and assess improvements relative to their counterparts for the earlier CMIP3. We find more than half of the models show improvements from CMIP3 to CMIP5 in simulating column-integrated cloud amount, while changes in water vapor simulation are insignificant. For the 19 CMIP5 models, the model spreads and their differences from the observations are larger in the upper troposphere (UT) than in the lower or middle troposphere (L/MT). The modeled mean CWCs over tropical oceans range from ∼3% to ∼15× of the observations in the UT and 40% to 2× of the observations in the L/MT. For modeled H2Os, the mean values over tropical oceans range from ∼1% to 2× of the observations in the UT and within 10% of the observations in the L/MT. The spatial distributions of clouds at 215 hPa are relatively well-correlated with observations, noticeably better than those for the L/MT clouds. Although both water vapor and clouds are better simulated in the L/MT than in the UT, there is no apparent correlation between the model biases in clouds and water vapor. Numerical scores are used to compare different model performances in regards to spatial mean, variance and distribution of CWC and H2O over tropical oceans. Model performances at each pressure level are ranked according to the average of all the relevant scores for that level.

Description: Journal of the American Chemical Society DOI: 10.1021/ja304315e

Description: ABSTRACT The objective of this paper is to understand the response of upper tropospheric (UT) clouds and water vapour (H 2 O) to sea surface temperature (SST) changes over the Indian Ocean. UT ice water content (IWC) and H 2 O observed by Aura Microwave Limb Sounder (MLS) show dominant dipole mode variability over the Indian Ocean. This is characterized by the oscillating differences between the western and eastern Indian Ocean (WIO and EIO) with greater amplitude in September, October and November (SON) as compared with other seasons. We denote δX = X_WIO − X_EIO, with X being H 2 O and IWC at three UT levels (215, 147 and 100 hPa) or SST, following the documented definition for Indian Ocean Dipole (IOD). We find a strong positive correlation between δIWC at the three UT levels and δSST, and a relatively weak positive correlation between δIWC and Niño 3.4 SST, suggesting that the UT clouds over the Indian Ocean are largely controlled by the local thermally driven circulation, while teleconnection to El Niño and Southern Oscillation (ENSO) plays a secondary role. The change per degree of δSST for δIWC in SON is 5.5 mg m −3  C −1 at 215 hPa, 1.6 mg m −3  C −1 at 147 hPa and 0.13 mg m −3  C −1 at 100 hPa (i.e. 96% C −1 , 87% C −1 and 46% C −1 increase at 215, 147 and 100 hPa, respectively). We find 36% C −1 increase in δH 2 O at 215 hPa with increasing δSST, associated with a sharp contrast in convective strength (indicated by δIWC) over the Indian Ocean region. On the other hand, δH 2 O at 100 hPa decreases with increasing δSST because cold temperature is observed above convective clouds and 100 hPa H 2 O is largely controlled by temperature. The Niño 3.4 SST has a relatively weak positive (negative) correlation with δH 2 O at 215 hPa (100 hPa).

Description: Based on a simple linear regression approach, normalized event‐based (a) and annual aggregated (b) TC losses in China will be four times higher at the 1.5 °C warming level than in the reference period (1986–2005). Relative to the 1.5 °C warming level, TCs will become more frequent under the 2.0 °C scenario, especially along the southeast coast of China. Limiting global warming at 1.5 °C would avoid an estimated increase in TC losses of more than 120 billion CNY annually. Adverse impacts and increasing economic losses from tropical cyclones (TCs) are a major focus in respect to the potential global warming of 1.5 °C or even 2.0 °C. Based on observed meteorological data and county‐scale loss records, loss‐inducing rainfall and wind speed thresholds are identified using the regional climate model CCLM to project future TC events in China. An established damage function is combined with future gross domestic product predictions under five shared socio‐economic pathways. At the 1.5 °C warming level, normalized TC losses will be four times higher than in the reference period (1986–2005). At the 2.0 °C warming level, a sevenfold increase is projected. Relative to the 1.5 °C warming level, TCs will become more frequent under the 2.0 °C scenario, especially along the southeast coast of China. Nearly 0.2–0.5% of the increase in gross domestic product might be offset by TC losses between the 1.5 °C and 2.0 °C warming levels, and the single highest TC loss at 2.0 °C may double that at 1.5 °C, with a larger affected area and more severe rainstorms and wind speeds. Rainfall is attributed more often to TC losses than wind speed. Limiting global warming at 1.5 °C would avoid an estimated increase in TC losses of more than 120 billion CNY annually.