Low Water Vapor Content Research Articles

Stratospheric water vapor affecting atmospheric circulation

Water vapor plays an important role in many aspects of the climate system, by affecting radiation, cloud formation, atmospheric chemistry and dynamics. Even the low stratospheric water vapor content provides an important climate feedback, but current climate models show a substantial moist bias in the lowermost stratosphere. Here we report crucial sensitivity of the atmospheric circulation in the stratosphere and troposphere to the abundance of water vapor in the lowermost stratosphere. We show from a mechanistic climate model experiment and inter-model variability that lowermost stratospheric water vapor decreases local temperatures, and thereby causes an upward and poleward shift of subtropical jets, a strengthening of the stratospheric circulation, a poleward shift of the tropospheric eddy-driven jet and regional climate impacts. The mechanistic model experiment in combination with atmospheric observations further shows that the prevailing moist bias in current models is likely caused by the transport scheme, and can be alleviated by employing a less diffusive Lagrangian scheme. The related effects on atmospheric circulation are of similar magnitude as climate change effects. Hence, lowermost stratospheric water vapor exerts a first order effect on atmospheric circulation and improving its representation in models offers promising prospects for future research.

Infrared Spectroscopic Investigations of Calcium Oxalate Monohydrate (Whewellite) Dehydration/Rehydration

Variable-temperature infrared spectroscopy is employed to monitor molecular vibrations during dehydration of calcium oxalate monohydrate (COM) and hydration of anhydrous calcium oxalate (COA). A unique variable-temperature infrared spectroscopy approach combines precise sample temperature control and rapid (2 °C s−1) heating/cooling with high-sensitivity infrared analysis. Infrared spectra are obtained at specific isothermal sample temperatures, while applying linear temperature versus time heating and cooling ramps, and in coordination with programmed temperature steps. Spectrum vibration bands provide information regarding the symmetry and local environments of solid-state water molecules and oxalate anions. When COM is heated, water molecules liberated from different crystallographic sites are selectively detected. Subtle oxalate anion configuration changes associated with water losses are detected based on infrared vibration band shapes and wavenumber trends. Dehydration and rehydration processes occur at lower temperatures and over narrower temperature ranges than conventional thermal analysis methods because samples consist of thin layers of small particles. Reversible and irreversible sample changes are distinguished by using a step heating/cooling temperature program and spectral subtractions. COA temperature-dependent structure variations that occur while heating and cooling samples in an atmosphere with a low water vapor concentration are characterized.

Intercomparison of upper tropospheric and lower stratospheric water vapor measurements over the Asian Summer Monsoon during the StratoClim campaign

Abstract. In situ measurements in the climatically important upper troposphere–lower stratosphere (UTLS) are critical for understanding controls on cloud formation, the entry of water into the stratosphere, and hydration–dehydration of the tropical tropopause layer. Accurate in situ measurement of water vapor in the UTLS however is difficult because of low water vapor concentrations (<5 ppmv) and a challenging low temperature–pressure environment. The StratoClim campaign out of Kathmandu, Nepal, in July and August 2017, which made the first high-altitude aircraft measurements in the Asian Summer Monsoon (ASM), also provided an opportunity to intercompare three in situ hygrometers mounted on the M-55 Geophysica: ChiWIS (Chicago Water Isotope Spectrometer), FISH (Fast In situ Stratospheric Hygrometer), and FLASH (Fluorescent Lyman-α Stratospheric Hygrometer). Instrument agreement was very good, suggesting no intrinsic technique-dependent biases: ChiWIS measures by mid-infrared laser absorption spectroscopy and FISH and FLASH by Lyman-α induced fluorescence. In clear-sky UTLS conditions (H2O<10 ppmv), mean and standard deviations of differences in paired observations between ChiWIS and FLASH were only (-1.4±5.9) % and those between FISH and FLASH only (-1.5±8.0) %. Agreement between ChiWIS and FLASH for in-cloud conditions is even tighter, at (+0.7±7.6) %. Estimated realized instrumental precision in UTLS conditions was 0.05, 0.2, and 0.1 ppmv for ChiWIS, FLASH, and FISH, respectively. This level of accuracy and precision allows the confident detection of fine-scale spatial structures in UTLS water vapor required for understanding the role of convection and the ASM in the stratospheric water vapor budget.

Emissivity retrievals with FORUM's end-to-end simulator: challenges and recommendations

Abstract. Spectral emissivity is a key property of the Earth's surface, of which only very few measurements exist so far in the far-infrared (FIR) spectral region, even though recent work has shown that the FIR is important for accurate modelling of the global climate. The European Space Agency's 9th Earth Explorer, FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) will provide the first global spectrally resolved measurements of the Earth's top-of-the-atmosphere (TOA) spectrum in the FIR. In clear-sky conditions with low water vapour content, these measurements will provide a unique opportunity to retrieve spectrally resolved FIR surface emissivity. In preparation for the FORUM mission with an expected launch in 2027, this study takes the first steps towards the development of an operational emissivity retrieval for FORUM by investigating the sensitivity of the emissivity product of a full spectrum optimal estimation retrieval method to different physical and operational parameters. The tool used for the sensitivity tests is the FORUM mission's end-to-end simulator. These tests show that the spectral emissivity of most surface types can be retrieved for dry scenes in the 350–600 cm−1 region, with an absolute uncertainty ranging from 0.005 to 0.01. In addition, the quality of the retrieval is quantified with respect to the precipitable water vapour content of the scene, and the uncertainty caused by the correlation of emissivity with surface temperature is investigated. Based on these investigations, a road map is recommended for the development of the operational emissivity product.

Differential absorption lidar for water vapor isotopologues in the 1.98 µm spectral region: sensitivity analysis with respect to regional atmospheric variability

Abstract. Laser active remote sensing of tropospheric water vapor is a promising technology to complement passive observational means in order to enhance our understanding of processes governing the global hydrological cycle. In such a context, we investigate the potential of monitoring both water vapor H216O and its isotopologue HD16O using a differential absorption lidar (DIAL) allowing for ground-based remote measurements at high spatio-temporal resolution (150 m and 10 min) in the lower troposphere. This paper presents a sensitivity analysis and an error budget for a DIAL system under development which will operate in the 2 µm spectral region. Using a performance simulator, the sensitivity of the DIAL-retrieved mixing ratios to instrument-specific and environmental parameters is investigated. This numerical study uses different atmospheric conditions ranging from tropical to polar latitudes with realistic aerosol loads. Our simulations show that the measurement of the main isotopologue H216O is possible over the first 1.5 km of atmosphere with a relative precision in the water vapor mixing ratio of <1 % in a mid-latitude or tropical environment. For the measurement of HD16O mixing ratios under the same conditions, relative precision is found to be slightly lower but still sufficient for the retrieval of range-resolved isotopic ratios with precisions in δD of a few per mil. We also show that expected precisions vary by an order of magnitude between tropical and polar conditions, the latter giving rise to poorer sensitivity due to low water vapor content and low aerosol load. Such values have been obtained for a commercial InGaAs PIN photodiode, as well as for temporal and line-of-sight resolutions of 10 min and 150 m, respectively. Additionally, using vertical isotopologue profiles derived from a previous field campaign, precision estimates for the HD16O isotopic abundance are provided for that specific case.

The Potential of Satellite Sounding Observations for Deriving Atmospheric Wind in All-Weather Conditions

Atmospheric wind is an essential parameter in the global observing system. In this study, the water vapor field in Typhoon Lekima and its surrounding areas simulated by the Weather Research and Forecasting (WRF) model is utilized to track the atmospheric motion wind through the Farneback Optical Flow (OF) algorithm. A series of experiments are conducted to investigate the influence of temporal and spatial resolutions on the errors of tracked winds. It is shown that the wind accuracy from tracking the specific humidity is higher than that from tracking the relative humidity. For fast-evolving weather systems such as typhoons, the shorter time step allows for more accurate wind retrievals, whereas for slow to moderate evolving weather conditions, the longer time step is needed for smaller retrieval errors. Compared to the traditional atmospheric motion vectors (AMVs) algorithm, the Farneback OF wind algorithm achieves a pixel-wise feature tracking and obtains a higher spatial resolution of wind field. It also works well under some special circumstances such as very low water vapor content or the region where the wind direction is parallel to the moisture gradient direction. This study has some significant implications for the configuration of satellite microwave sounding missions through their derived water vapor fields. The required temporal and spatial resolutions in the OF algorithm critically determine the satellite revisiting time and the field of view size. The brightness temperature (BT) simulated through Community Radiative Transfer Model (CRTM) is also used to track winds. It is shown that the error of tracking BT is generally larger than that of tracking water vapor. This increased error may result from the uncertainty in simulations of brightness temperatures at 183 GHz.

Airborne Measurements of Contrail Ice Properties—Dependence on Temperature and Humidity

AbstractThe largest share in the climate impact of aviation results from contrail cirrus clouds. Here, the dependence of microphysical contrail ice properties and extinction on temperature and humidity is investigated. Contrail measurements were performed at various altitudes during the 2018 ECLIF II/NDMAX campaign with the NASA DC‐8 chasing the DLR A320. Ice number concentrations and contrail extinction coefficients are largest at altitudes near 9.5 km, typical for short‐ and medium‐range air traffic. At higher altitudes near 11.5 km, low ambient water vapor concentrations lead to smaller contrail particle sizes and lower extinction coefficients. In addition, contrails were detected below 8.2 km near the Schmidt‐Appleman contrail formation threshold temperature. Here, only a small fraction (<15%) of the emitted soot particles were activated into ice. Our observations enhance the understanding of contrail formation near the formation threshold and give a glimpse on the altitude dependence of climate‐relevant contrail properties.

Intra-Event Isotopic Changes in Water Vapor and Precipitation in South China

Synchronous observations of the isotopic composition of water vapor and precipitation for 24 rain events were performed. Rain events driven by low-level jets exhibited similar isotopic changes in precipitation and water vapor. The vertical activity of water vapor in convection causes the isotopic variation in precipitation to be opposite to that of water vapor. Isotopic changes of precipitation in low-pressure systems were partially synchronized with that of water vapor at high but not low water vapor concentrations. Changes in microphysical meteorological properties in stratiform precipitation give rise to different patterns of isotopic changes in water. The re-evaporation of raindrops can be determined by the enrichment ratio of heavy isotopes in the water under the cloud base, which is closely related to the raindrop radius. Stratiform precipitation, with small raindrop sizes, was prone to kinetic fractionation under the cloud base. The raindrop radius of low-level jets was small, favoring exchange with surrounding air and re-evaporation. The moist air mass in convection facilitates isotopic exchange of raindrops with surrounding water vapor, leading to low enrichment ratios. The lowest enrichment ratios in low-pressure systems were due to environments characterized by large-scale water vapor convergence.

Mechanisms of trace water vapor frosting on a cryogenic surface in nitrogen gas flow

Water vapor contamination control is currently one of the key technical issues faced in cryogenic wind tunnels. However, the behaviors and the underlying mechanisms of trace water vapor frosting under cryogenic conditions still remain unknown due to the extreme experimental conditions and difficulties in direct measurement. A computational fluid dynamics (CFD) model was developed for describing the frosting process of trace water vapor on a cryogenic surface in nitrogen gas flow. The calculated results were validated against published experimental data and showed good agreements. The macroscopic and local growth behaviors of the frost layer were further studied based on the validated model. The variation in the nitrogen gas density under cryogenic conditions and its impact on the frost layer properties were analyzed. The change in the nitrogen gas density displayed a major difference between the frosting under refrigeration temperature conditions and cryogenic conditions, and taking the nitrogen gas density as a constant like previous models would cause great deviations in the calculated frost layer properties. The influence of water vapor content on the frost properties was also investigated. The frost layer thickness showed less sensitivity to changes in the water vapor content compared to the frost weight deposited on per unit area of the cold surface and the frost layer density. The frost layer under extremely low water vapor content might still cause small levels of distributed roughness on the surfaces, thereby affecting the aerodynamic characteristics of the model in the cryogenic wind tunnel.

Water vapor effects on CO2 separation of amine‐containing facilitated transport membranes (AFTMs) module: mathematical modeling using tanks‐in‐series approach

AbstractAmine‐containing facilitated transport membranes (AFTMs) are emerging membranes and have great potential for CO2 capture. AFTMs are particularly suitable for humid flue gases, as water vapor enhances the facilitated transportation of CO2. However, there is a lack of mathematical models available to evaluate the impact of water vapor on CO2 separation performance for large‐scale membrane modules. Therefore, developing a mathematical model considering the water vapor effects is of great importance to guide the large‐scale applications of AFTMs for CO2 capture.In this study, a mathematical model using tanks‐in‐series approach for CO2 capture through AFTMs is proposed. In this model, the tanks‐in‐series approach can reflect the variable (water vapor‐dependent) gas permeance along the membrane module. Modeling results showed the necessity of considering the effect of water vapor content decline along the module. In addition, both increasing temperature and pressure primarily lead to a faster decline of relative humidity (RH) along the membrane module, resulting in an increase of CO2 recovery but a decrease of CO2 product purity. For a gas stream with relatively low water vapor content (<2% in this study), different H2O permeance has a minor effect on separation performance. Moreover, permeate gas with higher water vapor content as well as higher RH is considered more suitable for further treatment of second stage membrane separation. In conclusion, the proposed model provides insights for comprehensive parameter analysis of membrane CO2 capture simulation and could support the development of large‐scale AFTMs separation applications, particularly for systems design and more accurate performance estimation. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Mid-infrared atmospheric transmittance at 5100m-altitude Ali Observatory

Ali in Tibet, 5100 m above sea level, is one of the most suitable locations in the world for infrared spectral observations. The atmospheric transmittances at Ali Observatory and Mauna Kea Observatory were calculated by MODTRAN using radiosonde data. The results were 0.848 and 0.789 respectively which indicated better conditions at Ali Observatory. A self-made instrument with a 320×256-pixel HgCdTe infrared focal plane array and a 7.5-cm diameter telescope was utilized for the actual measurements. Without the help of standard stars, the on-site and real-time atmospheric transmittance can be obtained as 0.831 by fitting the relation between the measured atmospheric radiation intensity and the zenith angle based on radiation transfer equations. This paper firstly reports the atmospheric transmittance in the M’ band (4.605–4.755 μm) at the 5100 m-altitude Ali observatory by actual measurement. It shows that the high-altitude Ali observatory with sufficiently low water vapor content is suitable for observation in the mid-infrared bands.

Monitoring of Solar Irradiance in the High Andes

Solar radiation has been measured in the high Andes near Laguna Lejia (latitude 23° 26' 23.30" S, longitude 67° 38' 14.29" W) at an elevation of 4715m between December 2016 and December 2017. Irradiances were monitored in four wavelength channels: PAR (400-700nm), UV-A (315-400nm), UV-B (295-315nm) and short-wavelength UV-B (295-310nm) with a new radiometer. In addition, ambient temperatures were recorded. Record values have been found for PAR (exceeding 600Wm-2 ), UV-A (close to 95Wm-2 ), UV-B (3.13Wm-2 ) and short-wavelength UV-B (0.144Wm-2 ) during Austral spring. The winter irradiance values slightly exceeded 50% of these values. Maximal cloud effects due to multiple reflections were 45, 38, 32 and 35% higher than values under cloudless skies for PAR, UV-A, UV-B and short-wavelength UV-B, respectively. Record irradiance for this site shows a UV index reaching and exceeding 20, which is due to low solar zenith angles, the altitude, low water vapor and aerosol concentrations in the atmosphere as well as low total column ozone concentrations.

Optical depth measurements at 45 and 90 GHz in CASLEO

The optical depth at 45 and 90 GHz have been obtained from calibration data of two solar radio telescopes located in El Leoncito Astronomical Complex (CASLEO), during the years 2012–2013. The observed period and the temporal resolution of the measurements is sufficient to show seasonal patterns. Using the precipitable water vapor content (PWV) obtained with a Sun-photometer for aerosols measurements, it was found a good correlation of PWV with the optical depth in both frequencies. With the water vapor content and data from a meteorological station, the atmosphere over CASLEO was modeled using ATM 2009, an Earth’s atmospheric model. The results of the model allows to evaluate the range of optical depth measurements and to predict the contributions from H2O and O2, the main components of optical depth at these frequencies. It was found a reasonable agreement at 45 GHz when the PWV is lower than 5 mm, but notable discrepancies for the entire range of water vapor content at 90 GHz. An empirical relation is established between the water vapor contribution to the measured optical depth for the observed frequencies. Our results show that CASLEO, despite being a site with 2500 meters high, is appropriate for solar observations in the millimeter range and is still useful for observations in the submillimeter at the epoch of the year with low water vapor content.

Age of martian air: Time scales for martian atmospheric transport

The mean time since air in the Martian atmosphere was in the low-latitude boundary layer is examined using simulations of an idealized “mean age” tracer with the MarsWRF general circulation model. The spatial distribution and seasonality of the mean age in low- and mid-latitudes broadly follow contours of the mean meridional circulation, with the mean age increasing from 0 at the surface to a maximum of 60–100 sols in the upper atmosphere. Substantially older mean ages (exceeding 300 sols) are found in polar regions, with oldest ages in the lower atmosphere (10–100 Pa), above a near-surface layer with very young ages (around 20 sols). The annual maximum ages occur around the equinoxes, and the age in the polar lower atmosphere decreases during the autumn to winter transition. This autumn-winter decrease in age occurs because of mixing of polar and mid-latitude air when the polar vortex exhibits an annulus of high potential vorticity (PV) with a local minimum near the pole. There is no autumn-winter decrease and old ages persist throughout autumn and winter in simulations with CO2 phase changes disabled, and thus no latent heating, where there is a monopolar vortex (i.e., a monotonic increase in PV from equator to pole) forms. The altitudinal and seasonal variations in the mean age indicates similar variations in the transport of dust into polar regions and the mixing of polar air (with, e.g., low water vapor and high ozone concentrations during winter) into mid-latitudes.

Detection flying aircraft from Landsat 8 OLI data

Monitoring flying aircraft from satellite data is important for evaluating the climate impact caused by the global aviation industry. However, due to the small size of aircraft and the complex surface types, it is almost impossible to identify aircraft from satellite data with moderate resolution, e.g. 30 m. In this study, the 1.38 μm water vapor absorption channel, often used for cirrus cloud or ash detection, is for the first time used to monitor flying aircraft from Landsat 8 data. The basic theory behind the detection of flying aircraft is that in the 1.38 μm channel most of the background reflectance between the ground and the aircraft is masked due to the strong water vapor absorption, while the signal of the flying aircraft will be attenuated less due to the low water vapor content between the satellite and the aircraft. A new composition of the Laplacian and Sobel operators for segmenting aircraft and other features were used to identify the flying aircraft. The Landsat 8 Operational Land Imager (OLI) 2.1 μm channel was used to make the method succeed under low vapor content. The accuracy assessment based on 65 Landsat 8 images indicated that the percentage of leakage is 3.18% and the percentage of false alarm is 0.532%.

Understanding the surface temperature cold bias in CMIP5 AGCMs over the Tibetan Plateau

The temperature biases of 28 CMIP5 AGCMs are evaluated over the Tibetan Plateau (TP) for the period 1979–2005. The results demonstrate that the majority of CMIP5 models underestimate annual and seasonal mean surface 2-m air temperatures (Tas) over the TP. In addition, the ensemble of the 28 AGCMs and half of the individual models underestimate annual mean skin temperatures (Ts) over the TP. The cold biases are larger in Tas than in Ts, and are larger over the western TP. By decomposing the Ts bias using the surface energy budget equation, we investigate the contributions to the cold surface temperature bias on the TP from various factors, including the surface albedo-induced bias, surface cloud radiative forcing, clear-sky shortwave radiation, clear-sky downward longwave radiation, surface sensible heat flux, latent heat flux, and heat storage. The results show a suite of physically interlinked processes contributing to the cold surface temperature bias. Strong negative surface albedo-induced bias associated with excessive snow cover and the surface heat fluxes are highly anticorrelated, and the cancelling out of these two terms leads to a relatively weak contribution to the cold bias. Smaller surface turbulent fluxes lead to colder lower-tropospheric temperature and lower water vapor content, which in turn cause negative clear-sky downward longwave radiation and cold bias. The results suggest that improvements in the parameterization of the area of snow cover, as well as the boundary layer, and hence surface turbulent fluxes, may help to reduce the cold bias over the TP in the models.

On the relative importance of radiative and dynamical heating for tropical tropopause temperatures

AbstractThe tropical tropopause layer (TTL) shows a curious stratification structure: temperature continues to decrease beyond the level of main convective outflow (∼200 hPa) up to the cold point tropopause (∼100 hPa), but the TTL is more stably stratified than the upper troposphere. A cold point tropopause well separated from the level of main convective outflow has previously been shown to be consistent with the detailed radiative balance in the TTL even without dynamical effects. However, the TTL is also controlled by adiabatic cooling due to large‐scale upwelling within the Brewer‐Dobson circulation, which creates the extremely low stratospheric water vapor content via freeze drying. Here we study the role of water vapor and ozone radiative heating on the detailed temperature structure of the TTL based on idealized single‐column radiative‐convective equilibrium simulations. An atmosphere without adiabatic cooling due to upwelling results in much higher stratospheric water vapor content; the resulting altered radiative heating structure is shown to push the TTL in a regime of radiative control by water vapor. The TTL structure is furthermore shown to be strongly sensitive to the altitude where ozone sharply transitions from tropospheric to stratospheric values. Adiabatic cooling due to upwelling is found to reduce the radiative control by water vapor, resulting primarily in a negative transport‐radiation feedback. Conversely, the radiative control by ozone is enhanced due to upwelling—a positive transport‐radiation feedback. The particularly strong ozone radiative effect may explain about half of the reported spread in cold point temperatures (∼10 K) in current climate models.

Estimating optical turbulence of atmospheric surface layer at Antarctic Taishan station from meteorological data

Turbulence intensity in the near-surface layer and its decrease rate with height are closely related to the quality of potential sites. Astronomers have been pursuing a perfect astronomical site to place the large-aperture telescopes. Compared with the best mid-latitude sites, Antarctic plateau inevitably becomes an ideal site for building the next-generation large optical and infrared telescopes, which is because of its low infrared sky emission, low atmospheric precipitable water vapour content, low aerosol and dust content of the atmosphere, and light pollution. In this paper, we establish a model of the atmospheric optical turbulence in surface layer, and use it to estimate Cn2 at Antarctic Taishan station for the first time. The meteorological parameters of the model input are the data measured by a mobile atmospheric parameter measurement system at Antarctic Taishan station from 30 December 2013 to 10 February 2014. The values of Cn2, estimated by the model and measured by a micro-thermometer, are compared. Sensitivity analysis of the estimation method is also carried out. The measurement results and analyses show that Cn2 obtained at Taishan station has obvious diurnal variation characteristics, with well-behaved peaks in the daytime and nighttime, and minima near sunrise and sunset. Cn2 obtained in the nighttime is stronger than that in daytime, more specifically, it is on the order of 210-14 m-2/3. The comparison between model predictions and experimental data demonstrates that it is feasible to estimate Cn2 in Antarctic by using this model. The biggest differences between Cn2 values obtained from the model and measurement usually emerge at sunrise and sunset, respectively. Considering the fact that Antarctic atmosphere is in a stable state most of the time, the values of Cn2 estimated by different nondimensional structure parameter functions are nearly the same. Thus, the measurement accuracy of air temperature difference from one height to another is the main factor that affects the estimated value of Cn2.

Monitoring of Arctic surface sudden warming events in late December 2015 with satellite remote sensing data

The explosively sudden warming of synoptic scale at the Arctic surface is often caused by meridional transport of lower latitude warm air or the ocean warm currents into the Arctic. The explosively sudden warming event that the Arctic surface temperature reached above 0°C on 29th December 2015 caused global concern. In the present paper, a variety of remote sensing data obtained by the AIRS (Atmospheric Infrared Sounder) flying on board NASA’s Aqua satellite were applied to monitor the abrupt changes in the atmospheric temperature, water vapor and ozone over the Flam Strait. AIRS measurements showed that the water vapor and temperature increased significantly beginning on December 27th, reached a peak on the 29th, then began to fall and oscillate, remaining above the December average value until January 2nd. At the same time, the atmospheric ozone showed the opposite change, having significantly reduced beginning on the 27th, and reached the minimum value on the 29th, after which it began to rebound and oscillate, then returned to near the December average value until January 2nd. The water vapor mainly changed from the surface to the 100 hPa height. On December 29th, the maximum increase of water vapor reached six times that of the December average at the 400 hPa height, the temperature changes mainly occurring from the surface to the 250 hPa height. The surface temperature reached to above 0°C on the 29th. The total amount of ozone changes became faster and greater. Compared to December 26th, the total amount of ozone reduced by 102 DU, thus reaching more than 1/3 of the December average. The ozone vertical profile mainly changed at the 400–5 hPa height. Compared to the 27th, the reduction of the ozone vertical profile accounted for 80%–90% of the total amount at this height on December 29th. Using NCEP reanalysis data, further combined with HYSPLIT air mass backward trajectory tracking, the analysis showed that the functionary mechanism which caused the surface explosively sudden warming was that the North Atlantic low-pressure storms rapidly transported large amounts of warm and moist air at low latitudes to the Arctic, which led to a dramatic increase in the low layer temperature and water vapor content. Additionally, the atmosphere was transported from low latitudes to higher latitudes, thereby harmonizing with the vertical motion of the atmosphere from the low level to the upper level. This led to the dramatic changes in ozone distribution from the upper troposphere to the stratosphere, in turn resulting in dramatic changes in the total ozone and vertical profiles. A typical example of satellite remote sensing monitoring showed that it was the power transmission of the synoptic scale which caused the rapid and dramatic changes of heat, water vapor and ozone in the Arctic.

Role of Water Vapor Content in the Effects of Aerosol on the Electrification of Thunderstorms: A Numerical Study

We explored the role of the water vapor content below the freezing level in the response of idealized supercell storm electrical processes to increased concentrations of cloud condensation nuclei (CCN). Using the Weather Research and Forecasting model coupled with parameterizations electrification and discharging, we performed 30 simulations by varying both the CCN concentration and water vapor content below the freezing level. The sensitivity simulations showed a distinct response to increased concentrations of CCN, depending on the water vapor content below the freezing level. Enhancing CCN concentrations increased electrification processes of thunderstorms and produced a new negative charge region above the main positive charge center when there were ample amounts of water vapor below the freezing level. Conversely, there were weak effects on electrification and the charge structure in numerical experiments initialized with lower water vapor content below the freezing level.