Nanjing University of Information Science and Technology

About: Nanjing University of Information Science and Technology is a education organization based out in Nanjing, China. It is known for research contribution in the topics: Precipitation & Aerosol. The organization has 14129 authors who have published 17985 publications receiving 267578 citations. The organization is also known as: Nan Xin Da.

Evaluation of Version-7 TRMM Multi-Satellite Precipitation Analysis Product during the Beijing Extreme Heavy Rainfall Event of 21 July 2012

Abstract: The latest Version-7 (V7) Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) products were released by the National Aeronautics and Space Administration (NASA) in December of 2012. Their performance on different climatology, locations, and precipitation types is of great interest to the satellite-based precipitation community. This paper presents a study of TMPA precipitation products (3B42RT and 3B42V7) for an extreme precipitation event in Beijing and its adjacent regions (from 00:00 UTC 21 July 2012 to 00:00 UTC 22 July 2012). Measurements from a dense rain gauge network were used as the ground truth to evaluate the latest TMPA products. Results are summarized as follows. Compared to rain gauge measurements, both 3B42RT and 3B42V7 generally captured the rainfall spatial and temporal pattern, having a moderate spatial correlation coefficient (CC, 0.6) and high CC values (0.88) over the broader Hebei, Beijing and Tianjin (HBT) regions, but the rainfall peak is 6 h ahead of gauge observations. Overall, 3B42RT showed higher estimation than 3B42V7 over both HBT and Beijing. At the storm center, both 3B42RT and 3B42V7 presented a relatively large deviation from the temporal variation of rainfall and underestimated the storm by 29.02% and 36.07%, respectively. The current study suggests that the latest TMPA products still have limitations in terms of resolution and accuracy, especially for this type of extreme event within a latitude area on the edge of coverage of TRMM precipitation radar and microwave imager. Therefore, TMPA users should be cautious when 3B42RT and 3B42V7 are used to model, monitor, and forecast both flooding hazards in the Beijing urban area and landslides in the mountainous west and north of Beijing.

Calibration of Suomi national polar-orbiting partnership advanced technology microwave sounder

Abstract: [1] The Suomi National Polar-Orbiting Partnership (NPP) satellite was launched on 28 October 2011 and carries the Advanced Technology Microwave Sounder (ATMS) on board. ATMS is a cross-track scanning instrument observing in 22 channels at frequencies ranging from 23 to 183 GHz, permitting the measurements of the atmospheric temperature and moisture under most weather conditions. In this study, the ATMS radiometric calibration algorithm used in the operational system is first evaluated through independent analyses of prelaunch thermal vacuum data. It is found that the ATMS peak nonlinearity for all the channels is less than 0.5 K, which is well within the specification. For the characterization of the ATMS instrument sensitivity or noise equivalent differential temperatures (NEDT), both standard deviation and Allan variance of warm counts are computed and compared. It is shown that NEDT derived from the standard deviation is about three to five times larger than that from the Allan variance. The difference results from a nonstationary component in the standard deviation of warm counts. The Allan variance is better suited than the standard deviation for describing NEDT. In the ATMS sensor brightness temperature data record (SDR) processing algorithm, the antenna gain efficiencies of main beam, cross-polarization beam, and side lobes must be derived accurately from the antenna gain distribution function. However, uncertainties remain in computing the efficiencies at ATMS high frequencies. Thus, ATMS antenna brightness temperature data records (TDR) at channels 1 to 15 are converted to SDR with the actual beam efficiencies whereas those for channels 16 to 22 are only corrected for the near-field sidelobe contributions. The biases of ATMS SDR measurements to the simulations are consistent between GPS RO and NWP data and are generally less than 0.5 K for those temperature-sounding channels where both the forward model and input atmospheric profiles are reliable.

Radiative Forcing and Health Impact of Aerosols and Ozone in China as the Consequence of Clean Air Actions over 2012–2017

Abstract: We applied the chemical transport model GEOS‐Chem to examine the changes in aerosols and tropospheric O3 in China from 2012–2017 and the associated radiative forcing and health impact. Simulated surface layer concentrations and column burdens of aerosols and O3 were evaluated by comparing with ground‐based and satellite‐retrieved measurements. Between 2012 and 2017, simulated annual mean concentrations of PM2.5 decreased by 21.0%, while O3 increased by 11.9% over eastern China (20–45°N, 105–122.5°E). Changes in aerosols and O3 over 2012–2017 jointly exerted a positive radiative forcing of 1.26 W/m over eastern China, which was dominated by the less cooling from PM2.5 reductions (1.18 W/m ). The Global Exposure Mortality Model predicted 268.3 (247.3–291.6) thousand (9.6%) fewer deaths in eastern China in 2017 relative to 2012. These results suggest an appreciable health benefit and a potential warming as a consequence of clean air actions. Plain Language Summary Stringent clean air actions have been implemented in China since 2013, aiming to improve air quality. As a result, observed concentrations of aerosols decreased while those of O3 increased in eastern China. In this work we assess the radiative forcing and health impact resulted from the changes in aerosols and O3 in China for the period of 2012–2017 by using a chemical transport model. The model reproduces the observed changes in PM2.5 and O3 in recent years and estimates a net positive radiative forcing of 1.26 W/m in 2017 relative to 2012 over eastern China. Further estimates from the mortality model show that approximately 270,000 deaths are avoided. Results from our study suggest an appreciable health benefit as well as a potential warming as a consequence of clean air actions over 2012–2017.

A Novel Reconfigurable Feeding Network for Quad-Polarization-Agile Antenna Design

Abstract: In this communication, a reconfigurable feeding network is proposed for the design of a quad-polarization-agile antenna. By switching the PIN diodes, the four transmission modes with selected phase differences can be electrically tuned at two output ports. For each mode, the measured insertion loss of the feeding network is less than 0.8 dB at the operating frequency. Because of its compact size, the proposed feeding network can be further integrated with a dual-polarized aperture-coupled antenna, which can exhibit two orthogonal linear polarizations and two orthogonal circular polarizations. Measured results of the polarization-agile antenna are shown in detail, which verify its performance.