Comparison of long-term total ozone observations from space-and ground-based methods at Zhongshan Station,Antarctica

Total ozone errors for satellite observations at Zhongshan Station in Antarctica are characterized using their relative difference （RD） from ground-based Brewer observations during 1993-2015. All satellite total ozone observations slightly overestimated ground-based ones （with RD less than 4%）. This is in contrast to conclusions drawn from global-scale validation studies, where main ground-based reference stations are located in middle latitudes. Given multiple total ozone data per day at Zhongshan Station, observed by a sun synchronous orbit satellite, measurements at the lowest solar zenith angle （SZA） show greatest consistency with Brewer ones, having an overall RD of-0.02-1.15%. Algorithm-retrieved total ozone data from the Total Ozone Mapping Spectrometer （TOMS）, including Solar Backscatter Ultra Violet （SBUV）, TOMS-Earth Probe （EP）, Ozone Monitoring Instrument （OMI）-TOMS, show best agreement with ground-based values; followed by the Global Ozone Measurement Experiment-type Direct Fitting （GOD-FIT） algorithm for the GOME-2A, and finally the Differential Optical Absorption Spectroscopy （DOAS） --Algorithm retrieved products for satellites-detectors of Global Ozone Measurement Experiment （GOME）, Scanning Imaging Absorption spectroMetr for Atmospheric CHartographY （SCIAMACHY）, and OMI. Satellite total ozone RD presents some statistical characteristics, but no specific trends. DOAS and GOME-2A algorithms have values that significantly increase, when the SZA is above 60°-70°, whereas values for GOME-2A decrease, when the SZA is 80-85°. Satellite total ozone RD is a minimum, when the Brewer total ozone is 300-350 DU, with an obvious increase in RD values for DOAS- and GOME-2A, when the Brewer total ozone is 150-300 DU. Satellite total ozone RD obviously increases, as the time difference between satellite overpasses and Brewer measurements grows. Specifically, RD rises as the absolute time difference increases to more than 4 h, yielding an OMI-TOMS RD of more than 10% as this difference increases to 8 h. The DOAS- RD may be up to 15%, while GOME-2A RD does not exceed 10%. The satellite total ozone RD may reach -5%, as the distance between the satellite overpass pixel and the station become more than 100 km. Possibly because of the discrepancy in surface albedo, the TOMS-algorithm retrieved total ozone produced underestimation, when the pixel on the south-east side of the station （the Antarctica continent） is used, but overestimation on the north-west side of the station （the Indian Ocean）. Consistency between space and ground-based total ozone data is least for the ＂ozone hole＂. Typically, the RD of TOMS-algorittun retrieved total ozone is within 1%/10 yr. Thus, the SBUV and Brewer monthly averaged total ozone anomalies from 1996 to 2015 were 1%/10 yr and 0.9%/10 yr, respectively. Both indicate slight, but consistent, ozone layer recovery.

Operational Plan,Effect Verification,and Key Technical Settings for a Stadium-Scale Artificial Rain Reduction Experiment

To explore the key technologies of artificial weather modification for specific targets(e.g.,a stadium)and improve the efficiency of artificial rainfall modification for major events,this study conducts an artificial rainfall reduction experiment for the closing ceremony of Nanjing Youth Olympic Games on 28 August 2014.Satellite retrievals,radar observations,sounding data,and other sources of information as well as Cloud and Precipitation Accurate Analysis System(CPAS)are used in this study.The main conclusions are as follows.(1)On 28 August 2014,a large-scale cumulus cloud system with mixed-phase stratocumulus and stratus precipitation was observed.This system was influenced by the weak shear of a low-level trough and the precipitation was dominated by cold clouds with dry layers between clouds.Thereby,we adopted the crystal-priming over-catalytic hypothesis and conducted a rocket-catalytic rain abatement operation at a certain distance(100–25 km)from the stadium.Rocket shootings of different intensities were implemented for two echoes that affected the stadium successively(two rounds of 15 rocket shootings within15 min for an isolated weak echo IA;multiple rounds of 156 rocket shootings within 80 min for a strong echo IB).Amazingly,after the shootings with the catalysis in the air,reflectivity of the two echoes was reduced at all altitudes with the most significant reduction at the 2-km altitude,and the time needed for the obvious reduction was 40 min.The most obvious reduction of the two echoes then maintained for 60 and 53 min,respectively,and the operation time needed for the echo zone to recover after the stop of rocket shooting was 108 min for echo IA and 90 min for echo IB.The two echoes moving across the stadium during the time period of the closing ceremony(2000–2130 local time)were at their minimal strengths,with almost no echo over the target stadium.This demonstrates that the rocket shooting strategy of over-crystallization catalysis is effective,and the shooting site,time,and dose are reasonable.The following technical parameters were used during this experiment.At about 80–25 km away from the target stadium in the west,the rocket shooting lasted for 15–80 min and the doses were not less than 1 shot min~(-1)(1 shot min~(-1)for echo IA,2.25 shots min~(-1)for echo IB).The attenuation rate was 0.21 dBZ min~(-1)for the average 15 dBZ of echo IA.For the average 25 dBZ of echo IB,the attenuation rate was 0.27 dBZ min~(-1).The above technical settings helped achieve the goal of reducing rain over the stadium to almost zero for nearly 1-h period during the critical time of the event.

Using the GPS observations to reconstruct the ionosphere three-dimensionally with an ionospheric data assimilation and analysis system(IDAAS)

Using an international reference ionosphere(IRI)model as a background ionosphere and applying the Kalman filter to update the state with observations,we develop an ionosphere data assimilation analysis system(IDAAS)to reconstruct a three-dimensional(3D)ionosphere with the GPS slant TEC and ionosonde data over east-south Asia.The preliminary results with the GPS data collected over east-south Asia on 30 June 2005 showed that inversed slant TEC has very good correlation with the observations both for the GPS sites being and not being involved in reconstruction.The inversed NmF2 and vertical TEC both demonstrate great improvement of agreement with those observed from ionosondes and TOPEX satellite independently.