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Studies on the atmospheric structure over the Antarctic Plateau are important for better understanding the weather and climate systems of polar regions. In the summer of 2017, an observational experiment was conducted at Dome-A, the highest station in Antarctica, with a total of 32 profiles obtained from global positioning system (GPS) radiosondes. Based on observational data, the atmospheric temperature, humidity and wind structures and their variations are investigated, and compared with those from four other stations inside the Antarctic circle. Distinguished thermal and dynamic structures were revealed over Dome-A, characterized by the lowest temperature, the highest tropopause, the largest lapse rate and the most frequent temperature and humidity inversion. During the experiment, a prominent blocking event was identified, with great influence on the atmospheric structure over Dome-A. The blocking high produced a strong anticyclone that brought warm and moist air to the hinterland of the Antarctic Plateau, causing a much warmer, wetter and windier troposphere over the Dome-A station. Meanwhile, a polar air mass was forced out of the Antarctic, formed a cold surge extending as far as Southern New Zealand and affected the weather there. Our results proved that there would be a direct interaction between the atmosphere over the hinterland of the Antarctic Plateau and middle latitudes with the action of a blocking high. Further studies are needed to explore the interaction between the atmospheric systems over the Antarctic and middle latitudes under intense synoptic disturbance, with long-term data and numerical modeling.

Accurate parameters that describe land–air exchange processes are essential for studying and predicting atmospheric processes over the Tibetan Plateau. Radiation, atmospheric thermal and moisture conditions, and turbulent heat and momentum fluxes were measured in the Yarlung Zangbo River, southeast Tibet, in May–July 2013. Based on the data, land–air exchange parameters were derived over the grassland surface, including the aerodynamic roughness length z0m, thermal roughness length z0h, the excess resistance to heat transfer kB−1 (where k represents the von Kármán constant and B−1 represents the Stanton number), and momentum and heat transfer coefficients (CD and CH, respectively). The average z0m was 7.0 cm, with a standard deviation of 1.4 cm; these values are higher than those observed in the central and western plateau regions and may have been affected by the tall grass and bush surface covers that surrounded the observation site. The average kB−1 was 5.7 ± 1.8, which is higher than that in other plateau regions in the same season. The average CD during the observation period, (11.9 ± 1.6) × 10−3, is also higher than that of other plateau regions. The commonly used iterative scheme and three noniterative turbulent flux parameterization schemes were evaluated over southeast Tibet using the above observational data. Parameter CD was underestimated by most schemes, whereas CH was overestimated by all schemes. Additional studies suggested that the iterative scheme performed best in retrieving the land–air exchange parameters and can be applied over southeast Tibet.

In-situ field observations of vertical aerosol profiles for one month in complex terrain (Lushan Mountain, China) were carried out using a cable car, which resolved detailed vertical distributions of mountain aerosols with low-cost operation. Cable-car observations were conducted during the early morning and late afternoon, when mountain and valley winds dominated, respectively. The diurnal aerosol variations at the top and foot of Lushan Mountain were analyzed based on environmental and meteorological stations. The observations indicated that the mountain-valley breezes notably impacted the mountain-area aerosol distribution under weak weather conditions. More uniform aerosol profiles for the afternoon than the morning, with their decreasing rates of PM2.5 (particles with diameters less than 2.5 μm) were 1.64 and 2.28 μg m−3/100 m, respectively. The PM2.5/PM10 ratio at the mountain top increased from 0.69 to 0.81, and that at the mountain base decreased from 0.75 to 0.70 from morning to afternoon. The PM2.5 concentration decreased in and around Lushan Mountain from daytime to nighttime, with the impacted diameter of the 300-m topography line being smaller than ~5 km, while the concentration increased in Jiujiang City. The relative decreasing rate of PM2.5 was higher at the mountain top site (~20%) than at the base site (~2%) from daytime to nighttime. Moreover, uniform aerosol profiles could have been caused by regional transport through a relatively strong low-level synoptic flow (~5 m s−1) and the mountain's dynamic lifting effect.

In June 2013, a field experiment was conducted in Southeast Tibet in which the air temperature, moisture, and wind were measured by using a GPS sounding system. In the present study, based on these observations and ERA-Interim reanalysis data, the vertical structures of these atmospheric properties and the possible influence of the South Asian summer monsoon (SASM) were investigated. On average, the temperature had a lapse rate of 6.8℃km−1 below the tropopause of 18.0 km. A strong moisture inversion occurred at the near-surface, with a strength of 1.7 g kg−1 (100 m)−1 for specific humidity. During the observation period, the SASM experienced a south phase and a north phase in the middle and by the end of June, respectively. The monsoon’s evolution led to large changes in convection and circulation over Southeast Tibet, which further affected the local thermal, moisture, and circulation conditions. The strong convection resulted in an elevated tropopause height over Southeast Tibet during the north phase of the SASM, and the large-scale warm and wet air masses delivered by the monsoon caused high local temperature and moisture conditions.

The Tibetan Plateau has substantial impacts on the weather and climate of the Northern Hemisphere, due in large part to the thermal effects of the plateau surface. Surface temperature over the Tibetan Plateau is the most important parameter in determining these thermal effects. We present a method for verifying widely used reanalysis temperature products from NCEP-R2, ERA-Interim, and JRA-25 over the Tibetan Plateau, with the aim of obtaining a reliable picture of surface temperature and its changes over the plateau. Reanalysis data are validated against the topography elevation, satellite observations, and radiosonde data. ERA-Interim provides the most reliable estimates of Tibetan Plateau surface temperature among these three reanalyses. We therefore use this dataset to study the climatology and trends of surface temperature over the Tibetan Plateau. ERA-Interim data indicate a dramatic warming over the Tibetan Plateau from 1979 to 2010, with warming rates of 0.33°C per decade in annual mean temperature, 0.22°C per decade in summer and 0.47°C per decade in winter mean temperatures. Comparison with the results of previous studies suggests that surface warming over the Tibetan Plateau has accelerated during the past 30 years. This warming is distributed heterogeneously across the Tibetan Plateau, possibly due to topographic effects.

Observations have shown highly variable ozone depletion over the Antarctic in the 2000s, which could affect the long-term ozone trend in this region as well as the global ozone recovery. By using the total column ozone data (1979–2011), interannual variation of the springtime Antarctic ozone low is investigated, together with its relationship with the polar vortex evolution in the lower stratosphere. The results show that springtime Antarctic ozone depletion has continued in the 2000s, seemingly contradicting the consensus view of a global ozone recovery expected at the beginning of the 21st century. The spring Antarctic polar vortex in the lower stratosphere is much stronger in the 2000s than before, with a larger area, delayed breakup time, and greater longevity during 2000–2011. Further analyses show that the recent continuation of springtime Antarctic ozone depletion could be largely attributed to the abnormal variation of the Antarctic polar vortex.

A Tibetan ozone low was found in the 1990s after the Antarctic ozone hole. Whether this ozone low has been recovering from the beginning of the 2000s following the global ozone recovery is an intriguing topic. With the most recent merged TOMS/SBUV (Total Ozone Mapping Spectrometer/Solar Backscatter Ultra Violet) ozone data, the Tibetan ozone low and its long-term variation during 1979–2010 are analyzed using a statistical regression model that includes the seasonal cycle, solar cycle, quasi-biennial oscillation (QBO), ENSO signal, and trends. The results show that the Tibetan ozone low maintains and may become more severe on average during 1979–2010, compared with its mean state in the periods before 2000, possibly caused by the stronger downward trend of total ozone concentration over the Tibet. Compared with the ozone variation over the non-Tibetan region along the same latitudes, the Tibetan ozone has a larger downward trend during 1979–2010, with a maximum value of −0.40±0.10 DU yr−1 in January, which suggests the strengthening of the Tibetan ozone low in contrast to the recovery of global ozone. Regression analyses show that the QBO signal plays an important role in determining the total ozone variation over the Tibet. In addition, the long-term ozone variation over the Tibetan region is largely affected by the thermal-dynamical proxies such as the lower stratospheric temperature, with its contribution reaching around 10% of the total ozone change, which is greatly different from that over the non-Tibetan region.

To understand the local atmosphere and heat transfer and to facilitate the boundary-layer parameterization of numerical simulation and prediction, an observational campaign was conducted in the Eastern Himalayas in June 2010. The local atmospheric properties and near-surface turbulent heat transfers were analyzed. The local atmosphere in this region is warmer, more humid and less windy, with weaker solar radiation and surface radiate heating than in the Middle Himalayas. The near-surface turbulent heat transfer in the Eastern Himalayas is weaker than that in the Middle Himalayas. The total heat transfer is mainly contributed by the latent heat transfer with a Bowen ratio of 0.36, which is essentially different from that in the Middle Himalayas and the other Tibetan regions.

The South Asian summer monsoon (SASM) is the most important climate system in Asia. Using observational data from the HEST2006 (Himalayan Exchange between the Surface and Troposphere 2006) campaign and large-scale grid data, this paper analyzed the SASM impact on local meteorological parameters including radiation, temperature, humidity, and wind in the Himalayas. The SASM experienced one active and one break period during the HEST2006 campaign. The local meteorological parameters exhibit great differences between the active period and the break period of the SASM. The radiation fluxes are greater in the break period than in the active period. The air temperature and specific humidity are lower, but soil temperature and wind speed are higher in the break period than in the active period. Further analysis indicates that the SASM greatly affects the meteorological features of the Himalayan region.

The global spectral model (GSM) at T213 horizontal resolution with 31 vertical levels has been used operationally in the China National Meteorological Center (CNMC) since 2002. The results show that the GSM is skillful in predicting large-scale circulations because of both the high spatial resolution and the improved model physics. However, because of the low skill in predicting the tropical cyclone (TC) genesis, the model has low skill in predicting TC tracks. In order to improve the prediction skill for TC tracks, an asymmetric bogus vortex scheme was implemented in the CNMCs operational GSM, and has being run in an experimental mode in 2003 and in an operational mode since 2004.

[1] To understand the heat exchange processes in the Tibetan mountains, the near surface turbulent heat transfers are analyzed based on the observations in the Rongbuk Valley on the northern slope of Mt. Everest during the HEST2006 campaign from June 1 to 29, 2006. The turbulent heat transfers are directed from the surface to the atmosphere in this valley. The averaged total heat flux is 102.1 W/m2, with a Bowen ratio of 2.17. This heat transfers are closely related to the south Asian summer monsoon (SASM) activities, with a large flux of 129.2 W/m2 during the SASM break period and a small flux of 79.8 W/m2 during the active period. The difference between the heat transfers of the two SASM periods is mainly caused by the enlarged sensible heat transfer in the SASM break period.

[1] Based on the observational data from the HEST2006 campaign in the Rongbuk Valley on the northern slope of Mt. Everest, in June, 2006, the variation of surface wind in the Rongbuk Valley and possible impact of the South Asian summer monsoon (SASM) on the surface wind are analyzed. During the observation campaign, SASM experienced a break stage and an active stage in middle and late June, 2006, respectively. The surface wind variation measured in the Rongbuk Valley is closely related to the SASM evolution, with a strong down-valley wind coinciding with the break stage of SASM and a weak down-valley wind with the active stage. It is suggested that the impact of SASM on the surface wind on the northern slope of Mt. Everest can be attributed to change of radiation conditions.

[1] The merged TOMS/SBUV ozone data for 1979–2002 are used to analyze, with a linear regression model and the other approaches, the zonal distribution of ozone variations between 50° and 60°N, the seasonal cycle and trends, and the responses to the solar cycle, quasi-biennial oscillation (QBO), El Nino–Southern Oscillation (ENSO) and Arctic Oscillation (AO). The seasonal ozone cycle shows ozone high over the north Pacific and low over the north Atlantic in winter, with a variability of 180 DU between 50° and 60°N. The maximum ozone trend obtained is over −5.3 ± 0.8%/decade at around 95°E in March. The anti-phase ozone response to the equatorial QBO is about 8 DU, with a 28-month period, in zonal average. In addition, the ozone responses to ENSO and AO are detected as 5 and 8 DU, respectively, between 95° and 190°E. The zonal inhomogeneity of ozone variations between 50° and 60°N is also discussed in this study.