Search Results

You are looking at 1 - 10 of 30 items for :

  • Author or Editor: Li Zhang x
  • Bulletin of the American Meteorological Society x
  • Refine by Access: All Content x
Clear All Modify Search
Nianliang Cheng, Yunting Li, Dawei Zhang, and Fan Meng
Full access
W. Paul Menzel, Timothy J. Schmit, Peng Zhang, and Jun Li

Abstract

Atmospheric sounding of the vertical changes in temperature and moisture is one of the key contributions from meteorological satellites. The concept of using satellite infrared radiation observations for retrieving atmospheric temperature was first proposed by Jean I. F. King. Lewis D. Kaplan noted that the radiation from different spectral regions are primarily emanating from different atmospheric layers, which can be used to retrieve the atmospheric temperature at different heights in the atmosphere. The United States launched the first meteorological satellite Television Infrared Observation Satellite-1 (TIROS-1) on 1 April 1960, opening a new era of observing the Earth and its atmosphere from space. Since then, hundreds of meteorological satellites have been launched by space agencies, including those in Europe, China, Japan, Russia, India, Korea, and others. With the rapid development of atmospheric sounding technology and radiative transfer models, it became possible to determine the atmospheric state from combined satellite- and ground-based measurements. With advances in computing power, forecast model development, data assimilation, and observing technologies, numerical weather prediction (NWP) has achieved consistently better results and thereby improved the prediction and early warning of severe weather events as well as fostered the initial monitoring of global climate change. The purpose of this paper is to summarize and discuss the development of satellite vertical sounding capability, quantitative profile retrieval theory, and applications of satellite-based atmospheric sounding measurements, with a focus on infrared sounding.

Open access
Qingxiang Li, Hongzheng Zhang, Xiaoning Liu, Ji Chen, Wei Li, and Phil Jones

Abstract

No Abstract available.

Full access
Xiaofeng Li, Jun A. Zhang, Xiaofeng Yang, William G. Pichel, Mark DeMaria, David Long, and Ziwei Li

In 2008, the Canadian Space Agency sponsored the Radarsat Hurricane Applications Project (RHAP), for researching new developments in the application of Radarsat-1 synthetic aperture radar (SAR) data and innovative mapping approaches to better understand the dynamics of tropical cyclone genesis, morphology, and movement. Although tropical cyclones can be detected by many remote sensors, SAR can yield high-resolution (subkilometer) and low-level storm information that cannot be seen below the clouds by other sensors. In addition to the wind field and tropical cyclone eye information, structures associated with atmospheric processes can also be detected by SAR. We have acquired 161 Radarsat-1 SAR images through RHAP between 2001 and 2007. Among these, 73 images show clear tropical cyclone eye structure. In addition, we also acquired 10 images from the European Space Agency's Envisat SAR between 2004 and 2010. Both Atlantic hurricanes and Pacific typhoons are included.

In this study, we analyze these 83 (73 Radarsat-1 and 10 Envisat) images with tropical cyclone eye information along with ancillary tropical cyclone intensity information from the archive to generate tropical cyclone morphology statistics. Histograms of wave-number asymmetry and intensity are presented. The statistics show that when the storm has higher intensity, the tropical cyclone eye tends to become more symmetric, and the area of the tropical cyclone eye, defined by the minimum wind area, tends to be smaller. Examples of finescale structures within the tropical cyclone (i.e., eye/eyewall mesovortices, arc clouds, double eyewalls, and abnormally high wind or rain within eyes) are presented and discussed.

Full access
Zhanshan Wang, Yunting Li, Tian Chen, Dawei Zhang, Lingjun Li, Baoxian Liu, Jinxiang Li, Feng Sun, and Libo Pan

Abstract

The Beijing government has made great effort to solve the air pollution problem in recent years. In this paper, the major air pollution control measures and the air quality improvement from 2008 to 2014 in Beijing were represented. With the implementation of a series of unconventional and high–air pollutant reduction measures in Beijing and the surrounding area, good air quality during both the 2008 Olympic Games and the 2014 Asia–Pacific Economic Cooperation (APEC) conference was guaranteed. Notably, a new scientific approach was applied to formulate air pollution control policy during the APEC conference. In addition to the established measures, two periods of enhanced and targeted reduction measures were implemented according to the forecast in advance. Finally, suggestions for improving air quality in Beijing were offered on the basis of the monitoring results and analyses during the APEC conference.

Full access
Jian Ling, Chongyin Li, Tim Li, Xiaolong Jia, Boualem Khouider, Eric Maloney, Frederic Vitart, Ziniu Xiao, and Chidong Zhang
Full access
Tim Li, Lu Wang, Melinda Peng, Bin Wang, Chidong Zhang, William Lau, and Hung-Chi Kuo

Abstract

The Madden–Julian oscillation (MJO) identified by Madden and Julian in the early 1970s has been well recognized as the most prominent intraseasonal signal in the tropics. Its discovery and its relationship with other weather phenomena such as tropical cyclones (TCs) are among the most significant advancements in modern meteorology with broad and far-reaching impacts. The original study by Madden and Julian used radiosonde data on Canton Island, and their spectral analysis revealed the signal of a 40–50-day oscillation.

It has come to our attention that an earlier study by Xie et al. published in a Chinese journal documented an oscillatory signal of a 45-day period using radiosonde data from several stations between 70° and 125°E in the tropics. The 40–50-day signal found by Xie et al. is strikingly evident without any filtering. Xie et al. identified that occurrences of TCs are correlated with the 40–50-day variation of low-level westerlies at these stations. The original figures in Xie et al.’s article were hand drawn. Their results are verified using data from a longer period of 1958–70. The 40–50-day oscillation in the monsoon westerlies and its relationship with the occurrence of TCs are confirmed and further expanded upon.

This study serves the purpose of bringing recognition to the community of the identification of a 40–50-day signal published in Chinese in 1963 and the discovery of the correlation between MJO phases and TC genesis three decades earlier than studies on this subject published outside China.

Open access
Qingxiang Li, Lei Zhang, Wenhui Xu, Tianjun Zhou, Jinfeng Wang, Panmao Zhai, and Phil Jones

Abstract

Time series of global or regional average surface air temperature (SAT) are fundamental to climate change studies. A number of studies have developed several national and regional SAT series for China, but because of the diversity of the meteorological observational sites, the different quality control routines for processing the data, and the inconsistency of the statistical methods used, they differ in their long-term trends. This paper assesses the similarities and differences of the existing time series of the annual average SAT for China that are based upon historical meteorological observations since the 1900s. The results indicate that the China average is similar to the series for the Northern Hemisphere (NH) landmass, except that the initial warming of the NH series derived from the CRUTEM3/4 datasets, which represent global historical land surface air temperatures and near-surface air temperature anomalies over land, respectively, ends earlier (before the early 1940s) than in China’s series. A major difference among the existing China average time series is the 1940s warmth, a period when there were very few observations across the country because of World War II. The SAT anomalies for China during the 1930s to 1940s have been reduced by improved homogeneity assessment compared to previous estimates. The new improved time series is in better agreement with both the historical twentieth-century reanalysis data and the historical climate simulation of phase 5 of the Coupled Model Intercomparison Project (CMIP5) models. The new time series also shows the slowdown of the warming trend during the past 18 yr (1998–2015). The best estimate of a linear trend for increases in temperature with a 95% uncertainty range is 0.121° ± 0.009°C decade–1 for 1900–2015, indicating that the improved homogeneity assessment for China leads to a slightly greater trend than that based on raw data (0.107° ± 0.009°C decade–1).

Full access
X. Y. Zhang, Y. Q. Wang, W. L. Lin, Y. M. Zhang, X. C. Zhang, S. Gong, P. Zhao, Y. Q. Yang, J. Z. Wang, Q. Hou, X. L. Zhang, H. Z. Che, J. P. Guo, and Y. Li

Before and during the 2008 Beijing Olympics from June to September, ground-based and satellite monitoring were carried out over Beijing and its vicinity (BIV) in a campaign to quantify the outcomes of various emission control measures. These include hourly surface PM10 and PM2.5 and their fraction of black carbon (BC), organics, nitrate, sulfate, ammonium, and daily aerosol optical depth (AOD), together with hourly reactive gases, surface ozone, and daily columnar NO2 from satellite. The analyses, excluding the estimates from weather contributions, demonstrate that after the control measures, including banning ~300,000 “yellow-tag” vehicles from roads, the even–odd turn of motor vehicles on the roads, and emission reduction aiming at coal combustion, were implemented, air quality in Beijing improved substantially. The levels of NO, NO2, NOx, CO, SO2, BC, organics, and nitrate dropped by about 30%–60% and the ozone moderately increased by ~40% while the sulfate and ammonium exhibited different patterns during various control stages. Weather conditions have a great impact on the summertime secondary aerosol (~80% of total PM) and O3 formations over BIV. During the Olympic Game period, various atmospheric components decreased dramatically at Beijing compared to the same period in the previous years. This decrease was related not only to the implementation of rigorous control measures, but also to the favorable weather processes. The subtropical high was located to the south so that Beijing's weather was dominated by the interaction between a frequently eastward shifting trough in the westerlies and a cold continental high with clear to cloudy days or showery weather.

Full access
Wenxia Zhang, Wei Li, Lianhua Zhu, Yuanyuan Ma, Linyun Yang, Fraser C Lott, Chunxiang Li, Siyan Dong, Simon F B Tett, Buwen Dong, and Ying Sun
Free access