Jhoon Kim

Solar cycle variability of hot oxygen atoms at Mars

The population of hot oxygen atoms in the Martian exosphere is reexamined using newly calculated hot O production rates for both low and high solar cycle conditions. The hot oxygen production rates are assumed to result from the dissociative recombination of O2+ ions. These calculations take into account the calculated vibrational distribution of O2+ and the new measured branching ratios. Furthermore, these calculations also consider the variation of the dissociative recombination cross section with the relative speed of the participating ions and electrons, the rotational energy of the O2+ ions, and the spread of the ion and electron velocities. These production rates were next used in a two-stream model to obtain the energy dependent flux of the hot oxygen atoms as a function of altitude. Finally, the calculated flux at the exobase was input into an exosphere model, based on Liouvilles theorem, to calculate the hot oxygen densities as a function of altitude in the exosphere and the resulting escape flux. It was found that hot oxygen densities vary significantly over the solar cycle; the calculated densities vary from about 2×103 to 6×103 cm−3 at an altitude of 1000 km. The escape flux also varies from about 3×106 to 9×106 cm−2s−1.

Calculated ionization rates, ion densities, and airglow emission rates due to precipitating electrons in the nightside ionosphere of Mars

The calculations presented in this paper clearly establish that the electron fluxes measured by the HARP instrument, carried on board Phobos 2, could cause significant electron impact ionization and excitation in the nightside atmosphere of Mars, if these electrons actually do precipitate. The calculated peak electron densities were found to be about a factor of 2 larger than the mean observed nightside densities, indicating that if a significant fraction of the measured electrons actually precipitate, they could be the dominant mechanism responsible for maintaining the nightside ionosphere. The calculated zenith column emission rates of the O I 5577-A and 6300-A and CO Cameron band emissions, due to electron impact and dissociative recombination mechanisms, were found to be significant.

Hot Carbon Densities in the Exosphere of Venus

[1] The results of calculations of hot carbon densities in the exosphere of Venus are presented. The calculation is a two-step process. First a two-stream transport code is used to solve for the distribution function at the exobase, and then these results are used in a Liouville equation solution above the exobase. It is found that generally, photodissociation of carbon monoxide is the largest source of hot carbon atoms in the upper atmosphere of Venus, larger than dissociative recombination of CO + and significantly larger than the creation of hot carbon through collisions with hot oxygen atoms. It is also found that the high solar activity densities are about 4 times larger than those for the low solar activity case. The results of these calculations are compared with the densities calculated by Paxton [1983]. INDEX TERMS: 5405 Planetology: Solid Surface Planets: Atmospheres—composition and chemistry; 5435 Planetology: Solid Surface Planets: Ionospheres (2459); 6295 Planetology: Solar System Objects: Venus; 6026 Planetology: Comets and Small Bodies: Ionospheres—composition and chemistry; KEYWORDS: carbon, exosphere, Venus

Retrieving aerosol optical depth using visible and mid-IR channels from geostationary satellite MTSAT-1R

An algorithm to retrieve aerosol optical depth (AOD) from a geostationary earth orbit (GEO) satellite by using visible and mid‐infrared (mid‐IR) channels is presented. This algorithm allows us to monitor transport of aerosols in higher temporal resolution from space in East Asia where both natural and anthropogenic aerosols exist all year round. The AOD is retrieved from two channels of 0.67 and 3.7 µm on board a GEO satellite, MTSAT‐1R, by using the look up table (LUT) approach. To overcome limitations of previous single visible channel algorithms of GEO satellites in estimating surface reflectance based on clear‐sky assumptions over a 30 day period, the possibility of using a mid‐IR channel at 3.7 µm was investigated. With the aid of the mid‐IR channel over a restricted surface area, surface reflectance was better characterized; this leads to smaller errors in the AODs. The application of a mid‐IR channel in retrieving surface reflectance shows potential in retrieving more accurate AODs from GEO satellites and is complementary to the clear‐sky composite method. The limitations in applying the mid‐IR channel and its dependency on surface temperatures should be treated appropriately in order to avoid errors in AOD retrieval.

Assimilation of next generation geostationary aerosol optical depth retrievals to improve air quality simulations

Planned geostationary satellites will provide aerosol optical depth (AOD) retrievals at high temporal and spatial resolution which will be incorporated into current assimilation systems that use low-Earth orbiting (e.g., Moderate Resolution Imaging Spectroradiometer (MODIS)) AOD. The impacts of such additions are explored in a real case scenario using AOD from the Geostationary Ocean Color Imager (GOCI) on board of the Communication, Ocean, and Meteorology Satellite, a geostationary satellite observing northeast Asia. The addition of GOCI AOD into the assimilation system generated positive impacts, which were found to be substantial in comparison to only assimilating MODIS AOD. We found that GOCI AOD can help significantly to improve surface air quality simulations in Korea for dust, biomass burning smoke, and anthropogenic pollution episodes when the model represents the extent of the pollution episodes and retrievals are not contaminated by clouds. We anticipate future geostationary missions to considerably contribute to air quality forecasting and provide better reanalyses for health assessments and climate studies.

Effects of ozone and aerosol on surface UV radiation variability.

Global (direct+diffuse) spectral ultraviolet (UV, 290-363nm) and total ozone measurements made on the roof of the Main Science Building, Yonsei University at Seoul (37.57°, 128.98°E) were analyzed to quantify the effects of ozone and aerosol on the variability of surface erythemal UV (EUV) irradiance. The measurements have been made with a Brewer Spectrophotometer MKIV (SCI-TEC#148) and a Dobson Ozone Spectrophotometer (Beck#123), respectively, during 2004-2008. The overall mean radiation amplification factor, RAF(AOD, SZA) [23,24] due to total ozone (O(3)) (hereafter O(3) RAF) shows that 1% decrease in total ozone results in an increase of 1.18±0.02% in the EUV irradiance with the range of 0.67-1.74% depending on solar zenith angles (SZAs) (40-70°) and on aerosol optical depths (AODs) (<4.0), under both clear (cloud cover<25%) and all sky conditions. For the mean AOD, the O(3) RAFs(SZA) for both sky conditions increased as SZA increased from 40° to 60°, and then decreased for higher SZA 70°, where the patterns are consistent with results of the previous studies [2,10]. A similar analysis of the RAF(O(3), SZA) due to AOD (hereafter AOD RAF) under clear and all-sky conditions shows that on average, a 1% increase in AOD forces a decrease of 0.29±0.06% in the EUV irradiance with the maximum range 0.18-0.63% depending on SZAs and O(3). Thus, overall sensitivity of UV to ozone (O(3), RAF) was estimated to be about four times higher than to the aerosol (AOD RAF). At the mean O(3), the AOD RAFs(SZA) for both skies appears to be almost independent of SZAs. It is shown that the O(3) RAFs are nearly independent of the sky conditions, whereas the AOD RAFs depend distinctly on the sky conditions with the larger values for all skies. Under cloud free conditions, the overall mean ratio for measured-to-modeled O(3), RAF(AOD, SZA) is 1.13, whereas the ratio for AOD RAF(O(3), SZA) shows 0.82 in the EUV irradiance. Overall, the RAF measurements are corroborated by radiative transfer model calculations under clear-sky conditions.

A two dimensional shock capturing, hydrodynamic model of the Venus ionosphere

A two-dimensional, time-dependent, shock capturing single-species (O+) hydrodynamic model of the Venus ionosphere, which solves the coupled continuity, momentum and energy equations for the altitude range of 150–500 km and the solar zenith angle range of 0°–180° has been developed and is presented in this paper. It was again demonstrated that the introduction of topside heat inflows leads to calculated dayside electron and ion temperatures, which are consistent with the measured values. In order to reproduce the measured electron temperatures, which are roughly constant over all SZAs, the heat inflows had to be reduced significantly over the nightside compared to the dayside values. The calculated transterminator ion flows are supersonic and relatively close to the observed average values. The model predicts a deceleration shock at a SZA of about 135°, consistent with the ion temperature and velocity observations.

The perception threshold measurement can be a useful tool for evaluation of sensitive skin

Sensitive skin is characterized by subjective symptoms that are hard to quantify. However, a neurobiological approach could improve our understanding of the nature of skin sensitivity. In this study, we measured the sensory perception of well‐controlled electric currents on the skin that stimulated sensory nerve fibres such as the myelinated A fibre, A delta fibre and unmyelinated c‐fibre. The sensory perception thresholds were obtained quantitatively from subjects with sensitive‐prone skin and controls. Application of 0.075% capsaicin, known to stimulate the nociceptor c‐fibre, was topically applied; then the sensory perception thresholds were measured to determine whether the exposure to nociceptive stimulation could affect the subsequent sensory perception. The results showed that the perception thresholds of skin sensitive‐prone subjects were low for the c‐fibre measurements at 5 Hz electric current stimulation. Furthermore, a wide variation in sensory perception was noted in the skin sensitive‐prone subjects after topical application of capsaicin. In conclusion, the abnormal sensory perception in individuals with sensitive skin appears to be related to neurological instability, where c‐fibre nociception plays a role. Thus, quantitative sensory perception threshold measurement was found to be a useful method for the identification of skin sensitive‐prone subjects.

Observation of secondary ozone peaks near the tropopause over the Korean peninsula associated with stratosphere‐troposphere exchange

[1] Vertical profiles of ozone partial pressure and temperature were obtained from ozonesonde measurements for 10 years from 1995 to 2004, over the midlatitude area at Pohang, Korea (36.02°N, 129.23°E), where stratosphere to troposphere exchange (STE) is very active. Secondary ozone peaks were observed in the upper troposphere/lower stratosphere at altitudes of about 14 km mostly in winter and spring. The 450 ozonesonde profiles were analyzed for this study together with satellite measurements from Halogen Occultation Experiment (HALOE) onboard the Upper Atmosphere Research Satellite (UARS). To compare with the satellite data sets, 188 HALOE data sets were archived over the period of 1993-2004 with extended locations for latitudes 32°N-40°N and longitudes of 120°E-135°E, which cover the Korean Peninsula region. The occurrence of secondary maxima in the upper troposphere is highly correlated with zonal wind speed and temperature enhancements. Most of these secondary peaks also were associated with stratosphere-troposphere exchange processes. The backward trajectory model, Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) from National Oceanic and Atmospheric Administration (NOAA) was used to examine these transport events further. The frequency of the secondary ozone peak appearance was found to increase at a rate of 1.4% yr -1 and 2.5% yr -1 for the past 10 years in this region on the basis of the ozonesonde and HALOE observations, respectively.

Recent Changes in Downward Longwave Radiation at King Sejong Station, Antarctica

Abstract Effects of cloud, air temperature, and specific humidity on downward longwave irradiance and their long-term variabilities are examined by analyzing the measurements made at the King Sejong Station in the Antarctic Peninsula during the period of 1996–2006. It has been shown that the downward longwave irradiance (DLR) is significantly correlated with three variables: air temperature, specific humidity, and cloudiness. Based on the relationship of the three variables with DLR, a multiple linear regression model has been developed in order to evaluate the relative contribution of each of the variables to the variation of DLR. The three variables together explained 75% of all the variance in daily mean DLR. The respective contribution from specific humidity and cloudiness to the variation of DLR was 46% and 23%; thus most of the DLR variability can be explained by the variations in the two variables. The annual mean of longwave cloud forcing shows 52 W m−2 with no remarkable seasonal cycle. It is als...