Siqi Zhang

Bio: Siqi Zhang is an academic researcher from China Meteorological Administration. The author has contributed to research in topics: Environmental science & Climatology. The author has an hindex of 3, co-authored 7 publications receiving 49 citations. Previous affiliations of Siqi Zhang include China University of Geosciences (Wuhan).

Global diurnal temperature range (DTR) changes since 1901

Abstract: Previous observational analyses show that the land-surface diurnal temperature range (DTR) has decreased in the past 6 decades worldwide. Based on a newly developed China Meteorological Administration–Land Surface Air Temperature (CMA-LSAT) dataset, we analyzed the DTR changes between 1901 and 2014. Results indicate that the global land surface DTR significantly decreased at a rate of − 0.036 °C decade− 1 over the 1901–2014 period, mainly due to the large decrease in DTR from 1951 to 2014. For the first half of the twentieth century, most grid boxes (spatial resolution 5° × 5°) show a positive DTR trend, with the positive trends of 32.4% grid boxes being statistically significant, leading to a large and significant increase of 0.048 °C decade− 1 in DTR. However, a dramatic reversal in DTR change occurred in early 1950s, with most parts of global lands exhibiting a shift from increasing to decreasing trends. The global land average DTR decrease during 1951–2014 was − 0.054 °C decade− 1, with 45.0% grid boxes showing significant negative trends. The reverse phenomenon is more obvious in the Northern Hemisphere than that in the Southern Hemisphere. For the periods 1979–2014 and 1998–2014, the decreasing trends in DTR mainly occur in the Northern Hemisphere. The DTR in the Southern Hemisphere experienced much larger increases during the two recent periods than during the period 1951–2014. Asia, Eastern North America, and Australia exhibited widespread decreases in DTR, although the trend pattern for global DTR is generally mixed during 1979–2014 and 1998–2014. There is a good negative correlation between DTR and precipitation in the Northern Hemisphere from 1901 to 2014, with a correlation coefficient of − 0.61. The change in precipitation and number of volcanic eruptions, and the “early brightening” of Europe (Stockholm) all benefit the increase of DTR at global and regional scales in the first half of the twentieth century.

Characteristics of Dry-Wet Climate Change in China during the Past 60 Years and Its Trends Projection

Abstract: Based on the homogenized daily data of 2255 meteorological stations during the past 60 years from 1961 to 2020, the potential evapotranspiration was calculated using the revised FAO56 Penman–Monteith model, and then the annual AI (aridity index, the ratio of annual potential evapotranspiration to annual precipitation) was employed to analyze the dry-wet climate change in China. The GCM models’ prediction data was used to analyze the possible trends of dry-wet climate in China by the end of this century. The results showed that in the past 60 years, the climate in China was getting wetter, especially in the western regions of China, including Xinjiang, western Qinghai, Gansu, western Inner Mongolia, and northwestern Tibet. In the last 10 years, China’s climate has become more humid. Compared with the 1960s, the total area of aridity has decreased by about 650,000 square kilometers. The changes of different climate zones have regional and periodical characteristics. There was a tendency to get wet periods in all four seasons, especially in summer. Analysis of GCM model projection data shows that by the end of this century, the climate in China would have a general trend of becoming drier. The drier regions are mainly located in the central and eastern parts of China, while the western regions of China continue to maintain the wetting trends. In the case of high emissions, the trends of drying in the central and eastern and wetting in the west are more significant than in the case of medium emission.

Comparison of Surface Air Temperature between Observation and Reanalysis Data over Eastern China for the Last 100 Years

Abstract: 27 This study aimed to improve understanding of the differences in surface air 28 temperature data between observations and reanalysis since the beginning of the 20th 29 century and to address the reanalysis data error. The anomaly correlation, standard 30 deviation, and linear trend of temperature during 1909–2010 in eastern China was 31 analyzed based on homogenized observation data from 16 stations and two sets of 32 20th century monthly mean surface air temperature reanalysis data (20CR and 33 ERA20C). The results show that the inter-annual and decadal variability were 34 consistent between reanalysis and observations in eastern China after 1979. The 35 reanalysis data exhibited a large fluctuation during the 1960s. The average 20CR 36 temperature was lower than the observations during 1920–1950. The inter-annual and 37 decadal variability for winter and spring were consistent with the observations. The 38 correlation and standard deviation ratio between the reanalysis and observations 39 demonstrated a high consistency of their inter-annual variability and dispersion. The 40 ERA20C data were generally closer to the observations than the 20CR data for the 41 period 1979–2010. The linear trends of surface air temperature showed clear warming 42 in both reanalysis datasets and the observations, but the reanalysis trends were 43 significantly smaller than the observational trends for annual mean temperature and 44 most of the seasonal mean temperatures after the 1950s. Overall, ERA20C was 45 generally closer to the observational temperatures than 20CR during 1909–2010, but 46 this consistency does not necessarily indicate ERA20C’s suitability for climate change 47 research because of the systematic bias referenced to the observational data. 48

On the Relationship Between Diurnal Temperature Range and Surface Solar Radiation in Europe

Abstract: [1] The surface solar radiation (SSR) is an important factor influencing the local and global energy budget. However, information on the spatial and temporal variation of SSR is limited. A more commonly available measure, which may provide such information, is the diurnal temperature range (DTR). In this study we analyze the relationship between DTR and SSR in Europe between 1970 and 2005 on seasonal and decadal scale. When comparing the mean anomalies time series composed of 31 pairs of sites with long-term SSR and DTR measurements, we found a correlation coefficient of 0.87 in the annual mean and between 0.61 and 0.92 in the seasonal mean anomalies. When investigating the individual pairs of SSR and DTR individually, we found that local correlations are mostly lower than the European mean and that they decrease rapidly in seasons and latitudes with low incident angles and at high alpine altitude. The highest correlation on local and seasonal scales seems to be connected with the variability of the large-scale circulation in Europe. The output of 11 simulations of current generation regional climate models over Europe confirms the strong relationship between SSR and DTR. The seasonal dependence of the relationship is well reproduced, but the absolute values of DTR and SSR are mostly too low. The pattern of decrease (dimming) and increase (brightening) in SSR and DTR was not reproduced in the modeled time series. There is still strong evidence from both models and observations that DTR is a reliable representative of SSR.

Estimation of urbanization bias in observed surface temperature change in China from 1980 to 2009 using satellite land-use data

Abstract: Since the 1980s, China has undergone rapid urbanization. Meanwhile, the climate has been warming substantially. In this paper, the urbanization effect on observed temperatures from 1980 to 2009 in China is estimated, based on analysis of urban land use from satellite observation. Urban land-use expansion (ΔU) during 1980–2005 is applied as an urbanization index. According to these ΔU values, stations are divided into three categories: (C1) intense urbanization around the stations; (C2) moderate urbanization around the stations; and (C3) minimal urbanization around the stations. Most C1 stations are in municipalities or provincial capitals, while C2 stations tend to be in prefecture-level cities. C3 stations are mostly in counties. The urban heat island (UHI) effect can be estimated if the urban effect on C3 is negligible. The warming of C1 or C2 relative to that of C3 represents their urbanization effects, assuming that the same larger-scale natural warming has affected each category. For C1, the local urbanization effect is 0.258°C/10 a over 1980–2009, accounting for 41% of the total warming; the trend at C2 is 0.099°C/10 a, or 21%. For all China, the urbanization effect is 0.09°C/10a, accounting for 20% of the total national warming. Winter urban warming is greater than in summer. The assumption of negligible urbanization effect on C3 is debatable, and so the true urbanization effect may equal or slightly exceed estimates. Further, the ΔU index may have some uncertainties, for it is only one of the urbanization indices. However, it provides a new and direct estimation of environmental change, in contrast to indirect indices.

The cause of decreased pan evaporation over the past 50 years

Abstract: Changes in the global water cycle can cause major environmental and socioeconomic impacts. As the average global temperature increases, it is generally expected that the air will become drier and that evaporation from terrestrial water bodies will increase. Paradoxically, terrestrial observations over the past 50 years show the reverse. Here, we show that the decrease in evaporation is consistent with what one would expect from the observed large and widespread decreases in sunlight resulting from increasing cloud coverage and aerosol concentration.