The probability distribution analysis is per-formed for multi-timescale aerosol optical depth (AOD) using AErosol RObotic NETwork (AERONET) level 2.0 data.The maximum likelihood estimation is employed to determine the...The probability distribution analysis is per-formed for multi-timescale aerosol optical depth (AOD) using AErosol RObotic NETwork (AERONET) level 2.0 data.The maximum likelihood estimation is employed to determine the best-fit probability density function (PDF),and the statement that the fitting Weibull distribution will be light-tailed is proved true for these AOD samples.The best-fit PDF results for multi-site data show that the PDF of AOD samples with longer timescale in most sites tends to be stably represented by lognormal distribution,while Weibull distribution is a better fit for AOD samples with short timescales.The reason for this difference is ana-lyzed through tail characteristics of the two distributions,and an indicator for the selection between Weibull and lognormal distributions is suggested and validated.The result of this research is helpful for determining the most accurate AOD statistics for a given site and a given time-scale and for validating the retrieved AOD through its PDF.展开更多
This paper focuses on the variability in entrainment rate in individual cumulus clouds using the entrainment rate estimated on the scale of 5 m in 186 shallow cumulus clouds from eight aircraft flights, using in situ ...This paper focuses on the variability in entrainment rate in individual cumulus clouds using the entrainment rate estimated on the scale of 5 m in 186 shallow cumulus clouds from eight aircraft flights, using in situ observations from the RACORO field campaign （the routine atmospheric radiation measurement aerial facility clouds with low optical water depths optical radiative observations） over the atmospheric radiation measurement Southern Great Plains site, USA. The result shows that the mean entrainment rate of all the 186 clouds systematically decreases from the cloud edge to the cloud center. Further analysis of the fluctuation of entrainment rate shows that the probability density function of entrainment rate in each flight can be fitted by the lognormal, gamma, or Weibull distributions virtually equally well, with the Weibull dis- tribution being the best. The parameter ＂standard devia- tion＂ in the lognormal distribution is weakly negatively correlated, and the other parameters in the three distribu- tions are positively correlated with relative humidity in the entrained dry air and dilution effect, respectively. Entrainment rate is negatively correlated with droplet concentration, droplet size, and liquid water content, but positively correlated with relative dispersion. The effect of entrainment rate on the spectral shape of cloud droplet size distribution is examined and linked to the systems theory on the cloud droplet size distribution.展开更多
Aims It is important to explore the underlying mechanisms that cause triphasic species–area relationship(triphasic SAR)across different scales in order to understand the spatial patterns of biodiversity.Methods Inste...Aims It is important to explore the underlying mechanisms that cause triphasic species–area relationship(triphasic SAR)across different scales in order to understand the spatial patterns of biodiversity.Methods Instead of theory establishment or field data derivation,I adopted a data simulation method that used the power function of SAR to fit log-normal distribution of species abundance.Important Findings The results showed that one-step sampling caused biphasic SAR and n-step sampling could cause 2n-phasic SAR.Practical two-step sampling produced triphasic SAR due to the Preston and Pan effects in large areas.Furthermore,before exploring biological or ecological mechanisms for the nature phenomenon,we should identify or exclude potential mathematical,statistical or sampling reasons.展开更多
Stars are born in dense cores of molecular clouds. The core mass function （CMF）, which is the mass distribution of dense cores, is important for understanding the stellar initial mass function （IMF）. We obtained ...Stars are born in dense cores of molecular clouds. The core mass function （CMF）, which is the mass distribution of dense cores, is important for understanding the stellar initial mass function （IMF）. We obtained 350μm dust continuum data using the SHARC-II camera at the Caltech Submillimeter Observatory （CSO） telescope. A 350μm map covering 0.25 deg2 of the Ophiuchus molecular cloud was created by mosaicing 56 separate scans. The CSO telescope had an angular resolution of 9＂, corresponding to 1.2 ×103 AU at the distance of the Ophiuchus molecular cloud （131 pc）. The data was reduced using the Comprehensive Reduction Utility for SHARC-II （CRUSH）. The flux density map was analyzed using the GaussClumps algorithm, within which 75 cores has been identified. We used the Spitzer c2d catalogs to separate the cores into 63 starless cores and 12 protostellar cores. By locating Jeans instabilities, 55 prestellar cores （a subcategory of starless cores） were also identified. The excitation temperatures, which were derived from FCRAO 12CO data, help to improve the accuracy of the masses of the cores. We adopted a Monte Carlo approach to analyze the CMF with two types of functional forms; power law and log-normal. The whole and prestellar CMF are both well fitted by a log-normal distribution, with p = -1. 18 ±0.10, σ = 0.58 ± 0.05 and μ= 1.40 ＋ 0.10, σ= 0.50 ＋ 0.05 respectively. This finding suggests that turbulence influences the evolution of the Ophiuchus molecular cloud.展开更多
基金supported by funds from the Chinese Global Change Research Program (Grant No.2010CB951804)the National Natural Science Foundation of China (Grant No.40830103)the China Postdoctoral Science Foundation (Grant No.20100480436)
文摘The probability distribution analysis is per-formed for multi-timescale aerosol optical depth (AOD) using AErosol RObotic NETwork (AERONET) level 2.0 data.The maximum likelihood estimation is employed to determine the best-fit probability density function (PDF),and the statement that the fitting Weibull distribution will be light-tailed is proved true for these AOD samples.The best-fit PDF results for multi-site data show that the PDF of AOD samples with longer timescale in most sites tends to be stably represented by lognormal distribution,while Weibull distribution is a better fit for AOD samples with short timescales.The reason for this difference is ana-lyzed through tail characteristics of the two distributions,and an indicator for the selection between Weibull and lognormal distributions is suggested and validated.The result of this research is helpful for determining the most accurate AOD statistics for a given site and a given time-scale and for validating the retrieved AOD through its PDF.
基金supported by the National Natural Science Foundation of China(41305120,91337215)the Research Foundation for Environmental Protection of Jiangsu Province(2013042)+9 种基金the Natural Science Foundation of Jiangsu Province,China(BK20130988)the Specialized Research Foundation for the Doctoral Program of Higher Education(20133228120002)the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province,China(13KJB170014)China Meteorological Administration Special Public Welfare Research Foundation(GYHY201406007)the Open Funding from State Key Laboratory of Severe Weather(2013LASW-B06)the Open Funding from Key Laboratory of Meteorological Disaster of Ministry of Education,China(KLME1305)the Qing Lan Projecta Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe US Department of Energy’s(DOE)Earth System Modeling(ESM)program via the FASTER project(www.bnl.gov/faster)Atmospheric System Research(ASR)Program
文摘This paper focuses on the variability in entrainment rate in individual cumulus clouds using the entrainment rate estimated on the scale of 5 m in 186 shallow cumulus clouds from eight aircraft flights, using in situ observations from the RACORO field campaign （the routine atmospheric radiation measurement aerial facility clouds with low optical water depths optical radiative observations） over the atmospheric radiation measurement Southern Great Plains site, USA. The result shows that the mean entrainment rate of all the 186 clouds systematically decreases from the cloud edge to the cloud center. Further analysis of the fluctuation of entrainment rate shows that the probability density function of entrainment rate in each flight can be fitted by the lognormal, gamma, or Weibull distributions virtually equally well, with the Weibull dis- tribution being the best. The parameter ＂standard devia- tion＂ in the lognormal distribution is weakly negatively correlated, and the other parameters in the three distribu- tions are positively correlated with relative humidity in the entrained dry air and dilution effect, respectively. Entrainment rate is negatively correlated with droplet concentration, droplet size, and liquid water content, but positively correlated with relative dispersion. The effect of entrainment rate on the spectral shape of cloud droplet size distribution is examined and linked to the systems theory on the cloud droplet size distribution.
基金The work was supported by the National Key R&D Program of China(2018YFF0214905 and 2016YFC1200802).
文摘Aims It is important to explore the underlying mechanisms that cause triphasic species–area relationship(triphasic SAR)across different scales in order to understand the spatial patterns of biodiversity.Methods Instead of theory establishment or field data derivation,I adopted a data simulation method that used the power function of SAR to fit log-normal distribution of species abundance.Important Findings The results showed that one-step sampling caused biphasic SAR and n-step sampling could cause 2n-phasic SAR.Practical two-step sampling produced triphasic SAR due to the Preston and Pan effects in large areas.Furthermore,before exploring biological or ecological mechanisms for the nature phenomenon,we should identify or exclude potential mathematical,statistical or sampling reasons.
基金by the California Institute of Technology under cooperative agreement with the National Science Foundation (Grant No. AST0838261)supported by National Basic Research Program of China (Grant No. 2012CB821800)+2 种基金National Aeronautics and Space Administration Undergraduate Student Research Program of USANational Natural Science Foundation of China (Grant Nos. 11373038 and 11163002)Graduate Innovative Fund of Gui Zhou University (Grant Nos. 2013024)
文摘Stars are born in dense cores of molecular clouds. The core mass function （CMF）, which is the mass distribution of dense cores, is important for understanding the stellar initial mass function （IMF）. We obtained 350μm dust continuum data using the SHARC-II camera at the Caltech Submillimeter Observatory （CSO） telescope. A 350μm map covering 0.25 deg2 of the Ophiuchus molecular cloud was created by mosaicing 56 separate scans. The CSO telescope had an angular resolution of 9＂, corresponding to 1.2 ×103 AU at the distance of the Ophiuchus molecular cloud （131 pc）. The data was reduced using the Comprehensive Reduction Utility for SHARC-II （CRUSH）. The flux density map was analyzed using the GaussClumps algorithm, within which 75 cores has been identified. We used the Spitzer c2d catalogs to separate the cores into 63 starless cores and 12 protostellar cores. By locating Jeans instabilities, 55 prestellar cores （a subcategory of starless cores） were also identified. The excitation temperatures, which were derived from FCRAO 12CO data, help to improve the accuracy of the masses of the cores. We adopted a Monte Carlo approach to analyze the CMF with two types of functional forms; power law and log-normal. The whole and prestellar CMF are both well fitted by a log-normal distribution, with p = -1. 18 ±0.10, σ = 0.58 ± 0.05 and μ= 1.40 ＋ 0.10, σ= 0.50 ＋ 0.05 respectively. This finding suggests that turbulence influences the evolution of the Ophiuchus molecular cloud.
