The accuracies of three instruments in measuring atmospheric column humidity were assessed during an upper troposphere and lower stratosphere observation campaign conducted from 7 to 13 August 2009 in Kunming, China. The three instruments are a cryogenic frost-point hygrometer (CFH), a Vaisala RS80 radiosonde (RS80), and a GTS1 radiosonde (GTS1). The accuracy of relative humidity (RH) measurements made by the CFH, GTS1, and RS80 was similar between the surface and 500 hPa (～5.5 km above sea level). However, above 500 hPa, the errors in RH measurements made by the RS80, relative to measurements made by the CFH, are much less than those detected with the GTS1. Three different retrieval methods for determining cloud boundaries from CFH, RS80, and GTS1 measurements were developed and take into account the differences in accuracy among the three instruments. The method for the CFH is based on RH thresholds at all levels, which demands high accuracy. Given that the accuracy of RH measurements decreases at higher altitudes, the cloud detection methods for RS80 and GTS1 are different for different altitude ranges. Below 5 km, the methods for the RS80 and the GTS1 are similar to that of the CFH; above 5 km, the methods for the RS80 and the GTS1 are both developed based on the second-order derivatives of temperature and RH with respect to height, but with different criteria applied. Comparisons of cloud-layer retrievals derived from the three measurements are also made.
The weekly averages of near-surface 7Be,210Pb,O 3,and CO2 concentrations at the Global Atmospheric Watch Observatory,Mt.Waliguan(101.98°E,36.287°N,3810 m a.s.l.) ,from October 2002 to January 2004 are presented.With the establishment of the new datasets of DCCW(Differential Concentrations in Contiguous Weeks) of 7Be,210Pb,and O 3,CO2(Δ7Be,Δ210Pb,ΔO3,ΔCO2,respectively,the impacts of upper-level downward transports and land-surface emissions on O3 and CO2 concentrations are implied by 7Be and 210Pb being as independent tracers.The relations amongΔ7Be,Δ210Pb,andΔO 3,ΔCO2 are examined statistically and compared.The results indicate that with the DCCWs,the interferences with the tracing significance of 7 Be and 210Pb from the seasonal wet scavenging of atmospheric aerosol are greatly reduced,and the weighting sources of O 3 or CO2 variations are more pronounced.Basically,the variability of surface O3 is controlled predominately by air mass transported from the upper atmosphere levels while the emission from the Continent Boundary Layer(CBL) has an obvious input for CO2.The relation betweenΔ210Pb andΔO3 reflects that influences of CBL emission are generally positive/negative for surface O3 budget in summer/winter,and the relation ofΔ7Be andΔCO2 also reveals that upper level downward transport has positive/negative inputs for CO2 in summer/winter.With the highly correlated relations between 7 Be and O3,a quantitative estimation is made of the stratospheric contributions to the budget of surface O3 at WLG:the monthly averages of stratospheric O3 range from 6×10 -9 to 8×10 -9(volume mixing ratio) in April and from June to August,and 2×10 -9 to 4×10 -9 in the remaining months.For the ultimate sources of the baseline concentration of surface O3,which consist of only stratospheric transport and tropospheric photochemistry production,the contribution from stratospheric transport is estimated to be about 20×10 -9 from May to July,and(12-15) ×10 -9 in the remaining months,and the total relative contribution
