Trends in Indices of Extreme Temperature and Precipitation in Iran over the Period 1960-2014

Climate extremes can have many negative effects on different sectors. Globally, observations show significant changes in the characteristics of extreme events. We examined trends in extreme temperature and precipitation indices in Iran during the period 1960-2014. We present results from 33 quality controlled and homogenous synoptic stations (excluding stations with excessive missing data). For each station, we calculate 27 indices characterizing extreme temperature and precipitation. For all indices (including Rx5DAY, CWD, R95p, R99p, GSL and TXn) positive, negative, and insignificant trends were obtained. Generally, there were negative trends in R10mm, R20mm, R25mm, CDD, PRCPTOT, FD, TN10p, TX10p, CSDI and positive trends in Rx1DAY, SDII, SU25, TR20, TXx, TNn, TNx, TN90p, TX90p and WSDI at most stations. There is a decreasing trend in the magnitude and frequency of cold extremes and an increasing trend in magnitude and frequency of warm extremes over the observational record, which is consistent with previous research reporting the warming trends of the climate.

GPS Water Vapor and Its Comparison with Radiosonde and ERA-Interim Data in Algeria

Remote sensing of atmospheric water vapor using global positioning system（GPS） data has become an effective tool in meteorology,weather forecasting and climate research. This paper presents the estimation of precipitable water（PW）from GPS observations and meteorological data in Algeria,over three stations located at Algiers,Bechar and Tamanrasset.The objective of this study is to analyze the sensitivity of the GPS PW estimates for the three sites to the weighted mean temperature（T;）,obtained separately from two types of T;–T;regression [one general,and one developed specifically for Algeria（T;stands for surface temperature）],and calculated directly from ERA-Interim data. The results show that the differences in T;are of the order of 18 K,producing differences of 2.01 mm in the final evaluation of PW. A good agreement is found between GPS-PW and PW calculated from radiosondes,with a small mean difference with Vaisala radiosondes.A comparison between GPS and ERA-Interim shows a large difference（4 mm） in the highlands region. This difference is possibly due to the topography. These first results are encouraging,in particular for meteorological applications in this region,with good hope to extend our dataset analysis to a more complete,nationwide coverage over Algeria.

Precipitation Regime Shift Associated with the Pacific Decadal Oscillation in the Maritime Continent

Recent changes in precipitation regime in South-East Asia are a subject of ongoing discussion. In this article, for the first time, evidence of a precipitation regime shift during the mid-1970s in the Northern Hemispheric part of South-East Asia is demonstrated. The detection of regime shifts is made possible by using a new comprehensive dataset of daily precipitation records (South-East Asian Climate Assessment and Dataset) and applying a novel Bayesian approach for regime shift detection. After the detected regime shift event in the mid-1970s, significant changes in precipitation distribution occurred in the Northern Hemispheric regions—Indochina Peninsula and the Philippines. More specifically, dry days became up to 10% more frequent in some regions. However, no precipitation regime shift is detected in Southern Hemisphere regions—Java and Northern Australia, were the number of observed dry days increased gradually.

A Late 20th Century European Climate Shift: Fingerprint of Regional Brightening?

We investigate the spatial extent of a statistically highly significant shift in atmospheric temperatures over Europe around 1987-1988 using a boot-strap change point algorithm. According to this algorithm, this change point (average warming of about one degree Celsius) is statistically highly significant (p > 99.9999%). The change point is consistently present in satellite and surface temperature measurements as well as temperature re-analyses and ocean heat content over most of Western Europe. We also find a connection with parts of the North Atlantic Ocean and eastern Asia. Although the time of change coincides with the North Atlantic Oscillation (NAO) going from negative to positive, the consistent warmer temperatures throughout the decades after 1987-1988 does not coincide with a persistent shift of the NAO, as it returns to a neutral/negative in the 1990’s. Furthermore, the shift does not coincide with any other known mode of multidecadal internal climate variability. We argue that the notion of a shift is “spurious”, i.e. the result of a fast change in Europe from dimming to brightening combined with an accidental sequence of cold (negative NAO) and warm (positive) NAO years during this period. The “shift” could therefore be considered as a fingerprint of European brightening during the last few decades.

Accelerations in the Local Magnetic Field on the Adriatic Tectonic Microplate

The high level of noise is a special feature of the geomagnetic field on the territory of Slovenia. The tension of the Adriatic tectonic microplate, on which Slovenia entirely lies, was recognized as one of its sources. The interior of the Earth is also the source of geomagnetic jerks. They are impulses in the secular variation calculated on the basis of monthly or annual mean values of variation of the geomagnetic field. The paper presents an analysis of accelerations in a local magnetic field calculated on the bases of daily mean values of the magnetic field measured at PIA geomagnetic Observatory (Piran, Slovenia) in 2020. These accelerations indicate geomagnetic impulses at the regional level over days or weeks. Then these results are compared with the registered seismic activity in the West Balkans.

Evaluation and comparison of CMIP6 models and MERRA-2 reanalysis AOD against Satellite observations from 2000 to 2014 over China

Rapid industrialization and urbanization along with a growing population are contributing significantly to air pollution in China.Evaluation of long-term aerosol optical depth(AOD)data from models and reanalysis,can greatly promote understanding of spatiotemporal variations in air pollution in China.To do this,AOD(550 nm)values from 2000 to 2014 were obtained from the Coupled Model Intercomparison Project(CIMP6),the second version of Modern-Era Retrospective analysis for Research,and Applications(MERRA-2),and the Moderate Resolution Imaging Spectroradiometer(MODIS;flying on the Terra satellite)combined Dark Target and Deep Blue(DTB)aerosol product.We used the TerraMODIS DTB AOD(hereafter MODIS DTB AOD)as a standard to evaluate CMIP6 Ensemble AOD(hereafter CMIP6 AOD)and MERRA-2 reanalysis AOD(hereafter MERRA-2 AOD).Results show better correlations and smaller errors between MERRA-2 and MODIS DTB AOD,than between CMIP6 and MODIS DTB AOD,in most regions of China,at both annual and seasonal scales.However,significant under-and over-estimations in the MERRA-2 and CMIP6 AOD were also observed relative to MODIS DTB AOD.The long-term(2000-2014)MODIS DTB AOD distributions show the highest AOD over the North China Plain(0.71)followed by Central China(0.69),Yangtse River Delta(0.67),Sichuan Basin(0.64),and Pearl River Delta(0.54)regions.The lowest AOD values were recorded over the Tibetan Plateau(0.13±0.01)followed by Qinghai(0.19±0.03)and the Gobi Desert(0.21±0.03).Large amounts of sand and dust particles emitted from natural sources(the Taklamakan and Gobi Deserts)may result in higher AOD in spring compared to summer,autumn,and winter.Trends were also calculated for 2000-2005,for2006-2010(when China introduced strict air pollution control policies during the 11 th Five Year Plan or FYP),and for 2011-2014(during the 12 th FYP).An increasing trend in MODIS DTB AOD was observed throughout the country during 2000-2014.The uncontrolled industrialization,urbanization,and rapid economic development that mostly occurred from 2000 to 2005 probably contributed to the overall increase in AOD.Finally,China’s air pollution control policies helped to reduce AOD in most regions of the country;this was more evident during the 12 th FYP period(2011-2014)than during the 11 th FYP period(2006-2010).Therefore this study strongly advises the authority to retain or extend these policies in the future for improving air quality.

Remote sensing and analysis of tropical cyclones:Current and emerging satellite sensors

This article describes recent advances in the capability of new satellite sensors for observing Tropical Cyclones(TC)fine structure,wind field,and temporal evolution.The article is based on a World Meteorological Organization(WMO)report prepared for the 10th International Workshop on Tropical Cyclones(IWTC),held in Bali in December 2022,and its objective is to present updates in TC research and operation every four years.Here we focus on updates regarding the most recent space-based TC observations,and we cover new methodologies and techniques using polar orbiting sensors,such as C-band synthetic aperture radars(SARs),L-band and combined C/X-band radiometers,scatterometers,and microwave imagers/sounders.We additionally address progress made with the new generation of geostationary and small satellites,and discuss future sensors planned to be launched in the next years.We then briefly describe some examples on how the newest sensors are used in operations and data assimilation for TC forecasting and research,and conclude the article with a discussion on the remaining challenges of TC space-based observations and possible ways to address them in the near future.

1743年华北夏季极端高温:相对温暖气候背景下的历史炎夏事件研究

根据中国历史气候记载和新近在欧洲发现的北京早期器测气象资料,研究1743年夏季华北高温极端气候事件,指出这是中国最近0.7ka来最严重的炎夏事件,高温区域广及北京、天津、河北、山西、山东.1743年7月北京的日最高气温高达44.4℃,超过了20世纪的极端气候记录.指出1743年的天气气候特征如旱涝分布、梅雨特点以及相应的太阳活动、海温场等外部因子条件,发现这些特征均与现代1942和1999年华北炎夏事件相同.该事件出现在气候相对温暖的背景下,是工业革命之前(CO2较低排放水平时)出现的极端高温实例.

基于随机森林模型的内陆干旱区植被指数变化与驱动力分析:以北天山北坡中段为例

全球变化背景下的干旱区植被变化受气候变化和人类活动双重影响。定量评价植被变化特征及其驱动机制,对监测干旱区区域生态环境变化,促进区域可持续发展有重要意义。由于复杂多样的人类活动难以量化,有关这方面的研究多局限于植被对气候变化的响应,而对人类活动影响考虑不足,导致关于这方面的认识存在较大的偏差和不确定性。该文首先提出与土地利用相关的人类活动量化表征方法;然后运用多元线性回归模型和随机森林模型中的较优模型,分析气候变化和具体的人类活动对北天山北坡中段归一化植被指数(NDVI)的影响。主要结果:(1) 2000–2015年期间北天山北坡中段年NDVI总体呈增加趋势;基于随机森林构建的NDVI与气候因子和人类活动的模型拟合精度明显优于多元线性回归模型,其决定系数(R2)至少提高了24%;(2)研究期内与耕地有关的人类活动对北天山北坡中段NDVI分布及时空变化的影响呈增加的特征,在2000–2015年期间人类活动对NDVI变化的贡献率为0.59,超过了气候因子。该项研究为气候变化和人类活动对植被的影响研究提供了新思路,也为干旱区生态环境保护和恢复提供了科学依据。

大气痕量气体差分吸收光谱仪云量反演算法研究

主要讨论O2-O2在477 nm处吸收带反演的有效云量。首先通过差分吸收光谱(DOAS)算法反演460~490 nm内的O2-O2斜柱浓度,并对O2-O2斜柱浓度中出现的条带进行修正;然后通过SCIATRAN辐射传输模型设置太阳天顶角、观测天顶角、相对方位角、地表反照率、地面高度、云量、云压等参数的不同节点,创建O2-O2斜柱浓度和反射率的查找表,进一步对查找表进行转换得到云量的查找表;最后对O2-O2斜柱浓度、连续反射率及相关太阳几何信息进行多维插值,得到大气痕量气体差分吸收光谱仪(EMI)有效云量。为验证所提算法的准确性,将EMI结果与OMI(ozone monitoring instrument)云量进行比较,两者均呈由低云量到高云量频数递减的趋势,其中云量为0和云量为1均出现频数高值现象,云量相关性R为0.82,相关性表现良好。

Hurricane eye morphology extraction from SAR images by texture analysis

Tropical hurricanes are among the most devastating hazards on Earth.Knowledge about its intense inner-core structure and dynamics will improve hurricane forecasts and advisories.The precise morphological parameters extracted from high-resolution spaceborne Synthetic Aperture Radar(SAR)images,can play an essential role in further exploring and monitoring hurricane dynamics,especially when hurricanes undergo amplification,shearing,eyewall replacements and so forth.Moreover,these parameters can help to build guidelines for wind calibration of the more abundant,but lower resolution scatterometer wind data,thus better linking scatterometer wind fields to hurricane categories.In this paper,we develop a new method for automatically extracting the hurricane eyes from C-band SAR data by constructing Gray Level-Gradient Co-occurrence Matrices(GLGCMs).The hurricane eyewall is determined with a two-dimensional vector,generated by maximizing the class entropy of the hurricane eye region in GLGCM.The results indicate that when the hurricane is weak,or the eyewall is not closed,the hurricane eye extracted with this automatic method still agrees with what is observed visually,and it preserves the texture characteristics of the original image.As compared to Du’s wavelet analysis method and other morphological analysis methods,the approach developed here has reduced artefacts due to factors like hurricane size and has lower programming complexity.In summary,the proposed method provides a new and elegant choice for hurricane eye morphology extraction.

基于大数据的全球城市扩展与土地覆盖动态遥感制图

Humans deeply influence the urbanizing of earth’s surface system in an exacerbating manner across space and time[1].Around the globe,urban land-use/cover changes reflect the intensities of human activities and land shifts from nature or semi-nature lands to man-made–dominated surfaces[2].

Canonical Workflows to Make Data FAlR

The FAIR principles have been accepted globally as guidelines for improving data-driven science and data management practices,yet the incentives for researchers to change their practices are presently weak.In addition,data-driven science has been slow to embrace workflow technology despite clear evidence of recurring practices.To overcome these challenges,the Canonical Workflow Frameworks for Research(CWFR)initiative suggests a large-scale introduction of self-documenting workflow scripts to automate recurring processes or fragments thereof.This standardised approach,with FAIR Digital Objects as anchors,will be a significant milestone in the transition to FAIR data without adding additional load onto the researchers who stand to benefit most from it.This paper describes the CWFR approach and the activities of the CWFR initiative over the course of the last year or so,highlights several projects that hold promise for the CWFR approaches,including Galaxy,Jupyter Notebook,and RO Crate,and concludes with an assessment of the state of the field and the challenges ahead.

Narrative warm/cold variations in continental western Europe, AD 708-1426

An extended narrative dataset of the Medieval time AD 708-1426 in continental western Europe was set up. Some 30-year-moving mean seasonal temperature deviation series were reconstructed. A warming trend occurred around AD 1200. During the warm stage, seasonal cycle might be weak due to frequent cool summers. Significant warm summer conditions did not occur until the late 14th century, when the annual temperature level began decreasing. The mean warm season temperature level during the late 14th to the early 15th century might be about 0.3℃ higher than the present. It was suggested to cautiously comment on historical climates for different seasons.

STUDY OF THE POSSIBILITIES OF USING AN AIR MASS TRANSFORMATION MODEL IN TAIYUAN

An AMT-model,consisting of a trajectory model and a one-dimensional boundary layer model,is tested for trajectories arriving in Taiyuan to study the possibility of using it in Taiyuan.The sensitivity of the model to the different processes was studied.Some parameters of the model were modified for the purpose of forecast- ing in specific mountainous terrain and dry climate conditions.Results of examples which we have worked out for Taiyuan circumstances for the periods of July(summer)1985 and January(winter)1986,show that the 12h runs of the AMT-model are able to reproduce(on historical data)the sounding of Taiyuan.The AMT-model contributes fruitfully to short-range weather forecasts(12—36h ahead)during periods of severe air pollution and when cold waves occur.

Direct Retrieval of NO_(2)Vertical Columns from UV-Vis(390-495nm)Spectral Radiances Using a Neural Network

Satellite retrievals of columnar nitrogen dioxide(NO_(2))are essential for the characterization of nitrogen oxides(NO_(x))processes and impacts.The requirements of modeled a priori profiles present an outstanding bottleneck in operational satellite NO_(2)retrievals.In this work,we instead use neural network(NN)models trained from over 360,000 radiative transfer(RT)simulations to translate satellite radiances across 390-495nm to total NO_(2)vertical column(NO_(2)C).Despite the wide variability of the many input parameters in the RT simulations,only a small number of key variables were found essential to the accurate prediction of NO_(2)C,including observing angles,surface reflectivity and altitude,and several key principal component scores of the radiances.In addition to the NO_(2)C,the NN training and cross-validation experiments show that the wider retrieval window allows some information about the vertical distribution to be retrieved(e.g.,extending the rightmost wavelength from 465 to 495 nm decreases the root-mean-square-error by 0.75%)under high-NO_(2)C conditions.Applying to four months of TROPOMI data,the trained NN model shows strong ability to reproduce the NO_(2)C observed by the ground-based Pandonia Global Network.The coefficient of determination(R2,0.75)and normalized mean bias(NMB,-33%)are competitive with the level 2 operational TROPOMI product(R^(2)=0:77,NMB=−29%)over clear(geometric cloud fraction<0:2)and polluted(NO_(2)C≥7:5×10^(15)molecules/cm2)regions.The NN retrieval approach is~12 times faster than predictions using high spatial resolution(~3 km)a priori profiles from chemical transport modeling,which is especially attractive to the handling of large volume satellite data.