Atmospheric Temperature Variations Research Articles

Meteorological effects in the lower ionosphere as based on VLF/LF signal observations

Abstract. Very low and low frequency (VLF/LF) data recorded in the Far Eastern stations Petropavlovsk-Kamchatsky (158.92° E, 53.15° N), Yuzhno-Sakhalinsk (142.75° E, 46.95° N) and Yuzhno-Kurilsk (145.861° E, 44.03° N) are investigated to study the meteorological effects in the lower ionosphere. The results demonstrate the sensitivity of the VLF/LF signals to the variations of atmospheric pressure, humidity, wind velocity and temperature, and the VLF/LF record at the station of Yuzhno-Kurilsk is found to be most sensitive to those variations of atmospheric parameters. The region under consideration is characterized by high winter cyclonic activity in mid-latitudes and strong summer and autumn typhoon activity in low latitudes. VLF/LF signal variations during eight tropical cyclones (TCs) with different intensity are considered. Negative nighttime anomalies in the signal amplitude that are most probably caused by TC activity are found for six events. Those anomalies are observed during 1–2 days when TCs move inside the sensitivity zones of the subionospheric paths. Perturbations of the VLF signal observed during two TCs can be caused by both the TC influence and seismic activity, but no correlation between TC intensity and magnitude of the signal anomalies is found. Spectral analysis of the typhoon-induced disturbed signals revealed the fluctuations with time periods in the range of 7–16 and 15–55 min that corresponds to the range of internal gravity waves periods.

Ozone distributions and urban air quality during summer in Agra – a world heritage site

Unplanned urban and industrial growth and rise in population are the main factors that had led to air pollution problems. Surface ozone causes human health problems and environmental degradation and acts as a greenhouse gas. Surface ozone is the most significant key substance of photochemical smog. Dependence of air pollutants on meteorology is described with the objective of understanding the prevailing processes pollutants phase interaction. Rigorous measurements of gaseous materials (surface O3, NO2, CO, and SO2) and particulate matter (PM2.5) were carried out regularly during the summer season of 2012 at kerbsite of Agra to assess the characteristics of air pollutants. The air mass trajectories have been calculated using the HYSPLIT 4 and FLEXTRA model. The maximum hourly levels of these pollutants exceeded 116.5 ppb for O3, 96.2 ppb for NO2, 16 ppb for SO2, 4.60ppm for CO and 188µg/m3 for PM2.5. There is obvious diurnal variation in the concentration of surface ozone which clearly follows the diurnal variation of atmospheric temperature. The joint application of principal component analysis and clustering techniques to data collected has led to the recognition of inherent relationships between variables that have been associated with governing processes related to surface O3 formation. The effect of wind on pollutants appears to be noteworthy. We also found that, the maximum average concentrations of SO2 and O3 occurred at humidity ≤30% pinpointing for strong vertical mixing. For CO, NO2 and PM2.5 the maximum average concentrations occurred at humidity below 40%.

Energy harvesting from atmospheric variations – Theory and test

The last two decades have offered a dramatic rise in the use of digital technologies such as wireless sensor networks that require small isolated power supplies. Energy harvesting, a method to gather energy from ambient sources including sunlight, vibrations, heat, etc., has provided some success in powering these systems. One of the unexplored areas of energy harvesting is the use of atmospheric temperature variations to obtain usable energy. This paper investigates an innovative device to extract energy from atmospheric variations using ethyl chloride filled mechanical bellows. The apparatus consists of a bellows filled with ethyl chloride working against a spring in a closed and controlled environment. The bellows expand/contract depending upon the ambient temperature and the energy harvested is calculated as a function of the bellows' length. The experiments showed that 6 J of energy may be harvested for a 23 °C change in temperature. The numerical results closely correlated to the experimental data with a deviation of 1%. In regions with high diurnal temperature variation, such an apparatus may yield approximately 250 μW depending on the ambient temperature range.

Climate and CO2 effects on the vegetation of southern tropical Africa over the last 37,000 years

The savanna vegetation of southern tropical Africa is characterized by co-dominance of C4 grasslands and C3 woodlands. Long-term variations in the tropical savanna vegetation in arid and semi-arid climates are commonly considered to be primarily sensitive to precipitation and atmospheric CO2 concentrations. The sensitivity of tropical vegetation to temperature, however, is often considered as secondary or negligible, particularly in paleostudies due to difficulties of reconstructing terrestrial temperature in the tropics. In this study, we use the terrestrial vegetation model BIOME4, which was forced by climate simulations from the Kiel Climate Model (KCM) for the Holocene and by climate reconstructions for the most recent glacial period to understand reconstructed vegetation changes in southern tropical Africa of the past 37,000 yr. We focus on these two periods because vegetation reconstructions from a marine sediment core near the Zambezi River mouth cannot be explained by precipitation changes and changes of atmospheric CO2 alone. For the Holocene, we force BIOME4 simulations with reconstructed atmospheric CO2 concentrations, and spatial and seasonal climate patterns from the early- and mid-Holocene (9.5 and 6 ka BP) simulations with the KCM. For the glacial period, we analyze idealized experiments based upon reconstructed temperature, precipitation and CO2 at 31, 28 and 21 ka BP. Our study shows that both Holocene and glacial simulations of vegetation cover exhibit good agreement with reconstructed C4:C3 ratios when temperature changes are taken into account. While both precipitation and temperature control the C4:C3 ratio during the Holocene atmospheric CO2 and temperature variations are major factors controlling vegetation changes during the glacial period. In our simulations, variations in temperature along with precipitation and atmospheric CO2 reconcile the evolution of vegetation observed in the Zambezi catchment during the last 37,000 yr. In consequence, the effect of temperature variations on tropical savanna vegetation should be taken into account with respect to modeling past or future climates.

Air–sea interactions during strong winter extratropical storms

A high-resolution, regional coupled atmosphere–ocean model is used to investigate strong air–sea interactions during a rapidly developing extratropical cyclone (ETC) off the east coast of the USA. In this two-way coupled system, surface momentum and heat fluxes derived from the Weather Research and Forecasting model and sea surface temperature (SST) from the Regional Ocean Modeling System are exchanged via the Model Coupling Toolkit. Comparisons are made between the modeled and observed wind velocity, sea level pressure, 10 m air temperature, and sea surface temperature time series, as well as a comparison between the model and one glider transect. Vertical profiles of modeled air temperature and winds in the marine atmospheric boundary layer and temperature variations in the upper ocean during a 3-day storm period are examined at various cross-shelf transects along the eastern seaboard. It is found that the air–sea interactions near the Gulf Stream are important for generating and sustaining the ETC. In particular, locally enhanced winds over a warm sea (relative to the land temperature) induce large surface heat fluxes which cool the upper ocean by up to 2 °C, mainly during the cold air outbreak period after the storm passage. Detailed heat budget analyses show the ocean-to-atmosphere heat flux dominates the upper ocean heat content variations. Results clearly show that dynamic air–sea interactions affecting momentum and buoyancy flux exchanges in ETCs need to be resolved accurately in a coupled atmosphere–ocean modeling framework.

Is global warming affecting cave temperatures? Experimental and model data from a paradigmatic case study

This research focuses on the mechanisms that transfer the variations in surface atmospheric temperature into caves to evaluate whether they record the warming trend of recent decades. As a study case, we use the data from a hall in Postojna Cave (Slovenia), which was monitored from 2009 to 2013. The low-frequency thermal variability of this cave chamber is dominated by the conduction of heat from the surface through the bedrock. We implemented a thermal conduction model that reproduces low-frequency thermal gradients similar to those measured in the cave. At the 37 m depth of this chamber, the model confirms that the bedrock is already recording the local expression of global warming with a delay of 20–25 years, and predicts a cave warming during the coming decades with a mean rate of 0.015 ± 0.004 C year−1. However, because of the transfer of surface atmosphere thermal variability depends on the duration of the oscillations, the thermal anomalies with periods 7–15 years in duration have delay times <10 years at the studied hall. The inter-annual variability of the surface atmospheric temperature is recorded in this cave hall, although due to the different delay and amplitude attenuation that depends on the duration of the anomalies, the cave temperature signal differs significantly from that at the surface. As the depth of the cave is a major factor in thermal conduction, this is a principal control on whether or not a cave has already recorded the onset of global warming.

Dependence of Small Internal Combustion Engine’s Performance on Altitude

The effects of atmospheric pressure and temperature variations on the performance of small internal combustion engines operating at altitudes significantly above sea level are not widely documented. Most small internal combustion engines are designed and manufactured for ground-based applications such as chainsaws and lawn mowers. However, these engines are finding application as power sources for remotely piloted aircraft for both hobbyist and military applications. A test stand with the capability to control atmospheric conditions was developed for representative small internal combustion engines. During previous research, data were recorded to identify the impact of varying engine intake pressure on engine performance both with a carburetor and with a throttle body fuel-injection system delivering a gasoline–oil mixture. Using the stand and fuel-injection system, data were collected while varying air temperature along with pressure. Results revealed a decrease in performance (power and brake mean effective pressure) of nominally 4% per 300 m of elevation due to pressure, while improvements of 1% per 300 m were due to temperature effects. This resulted in a nominal 3% loss per 300 m of altitude. These data were then used to establish an updated correction factor for power due to altitude changes. A speed-dependent model was validated for this small engine. These measurements provide a better understanding of small internal combustion engines operation at altitude. Quantifying these effects is vital for establishing the capability of operating spark-ignition engines at altitudes well above those for which they were designed.

The water dimer millimeter-wave spectrum at ambient conditions: A simple model for practical applications

A simple model of the water dimer millimeter-wave spectrum at pressures and temperatures typical of Earth׳s atmosphere is proposed. The model is based on high accuracy ab initio calculations and is supported by experimental observations of the dimer spectrum in cold molecular beams. It is demonstrated that the model corresponds to the spectra calculated ab initio and recorded at room temperature. The model is used for assessing atmospheric brightness temperature variations caused by the water dimer absorption. A possibility of direct radiometric observation of the dimer in the Earth׳s atmosphere is shown.

Development of operation and maintenance technology for HTGRs by using HTTR (High Temperature engineering Test Reactor)

To establish the technical basis of HTGR (High Temperature Gas cooled Reactor), the long term high temperature operation using HTTR was carried out in the high temperature test operation mode during 50-day since January till March, 2010. It is necessary to establish the technical basis of operation and maintenance by demonstrating the stability of plant during long-term operation and the reliability of components and facilities special to HTGRs, in order to attain the stable supply of the high temperature heat to the planned heat utilization system of HTTR. Test data obtained in the operation were evaluated for the technical issues which were extracted before the operation. As the results, it was confirmed that the temperatures and flow rate of primary and secondary coolant were well controlled within sufficiently small deviation against the disturbance by the atmospheric temperature variation in daily. Stability and reliability of the components and facility special to HTGRs was demonstrated through the long term high temperature operation by evaluating the heat transfer performance of high temperature components, the stability performance of pressure control to compensate helium gas leak, the reliability of the dynamic components such as helium gas circulators, the performance of heat-up protection of radiation shielding. Through the long term high temperature operation of HTTR, the technical basis for the operation and maintenance technology of HTGRs was established.

Exploration of regional surface average heat flow from meteorological and geothermal series

We attempt to compute the Surface Average Heat Flow (SAHF) from long-term temperature observations of one hundred seventy-seven observational points at the depths of 0.8, 1.6, and 3.2 m, which were relatively evenly distributed in mainland China. We first employ Fourier transformation to remove the influence of atmospheric temperature variations from the observation series, which are classified into the type of the steady-state temperature monotonously increasing with depth (type I) and other three types. Then we compare our results obtained from the data of type I, of which the values are thought to equal to those of the mean borehole heat flow, with those obtained from traditional heat flow observations mainly distributed in North China Craton. In computations of the SAHF at the observation stations, we deduce the thermal diffusivity and volumetric specific heat of the soil by employing harmonic solutions of the heat conduction equation for the same moisture group as the first step, and then we determine the SAHF using Fourier’s law. Our results indicate that the SAHF derived from shallow earth geothermal data can reflect the heat flow field to a large extent.

The Effect of Atmospheric Temperature and Pressure on the Occurrence of Acute Myocardial Infarction in Kaunas

OBJECTIVE. The aim of the study was to evaluate the impact of meteorological variables (atmospheric temperature and pressure) on the daily occurrence of acute myocardial infarction (AMI). MATERIAL AND METHODS. The study used the daily values of atmospheric temperature and pressure in 2000-2007. The meteorological data were obtained from the Lithuanian Hydrometeorological Service for Kaunas. The relative risks of event occurrence were computed for 5°C atmospheric temperature and for 10-hPa atmospheric pressure variations by means of the Poisson regression model. RESULTS. The occurrence of AMI and atmospheric temperature showed an inverse linear relationship, while the occurrence of AMI and atmospheric pressure, a positive linear relationship. Among the youngest subjects (25-44 years old), no relationships were detected. Contrary, among the subjects aged 45-64 years and those aged 65 years and older, the occurrence of AMI significantly decreased with higher temperature (P=0.001 and P=0.002, respectively). A decrease in atmospheric temperature by 10ºC reduced the risk of AMI by 8.7% in the age groups of 45-64 and 65 years and older and by 19% in the age group of 25 years and older. Among the first AMI cases, the risk increased by 7.5% in the age group of 45-64-year olds and by 6.4% in the age group of 25-64-year olds. The relationship between atmospheric temperature and pressure, and AMI occurrence was found to be linear but inverse. An increase in atmospheric pressure by 10 hPa resulted in an increase in risk by 4% among the subjects aged 65 years and more and by 3% among the subjects aged 25 years and more. CONCLUSIONS. Atmospheric temperature and pressure variations had the greatest effect on middle-aged and aging subjects (starting from 45 years). At younger age, the effect of such factors on the AMI risk was considerably lower.

Modeling the effects of fire severity and climate warming on active layer thickness and soil carbon storage of black spruce forests across the landscape in interior Alaska

There is a substantial amount of carbon stored in the permafrost soils of boreal forest ecosystems, where it is currently protected from decomposition. The surface organic horizons insulate the deeper soil from variations in atmospheric temperature. The removal of these insulating horizons through consumption by fire increases the vulnerability of permafrost to thaw, and the carbon stored in permafrost to decomposition. In this study we ask how warming and fire regime may influence spatial and temporal changes in active layer and carbon dynamics across a boreal forest landscape in interior Alaska. To address this question, we (1) developed and tested a predictive model of the effect of fire severity on soil organic horizons that depends on landscape-level conditions and (2) used this model to evaluate the long-term consequences of warming and changes in fire regime on active layer and soil carbon dynamics of black spruce forests across interior Alaska. The predictive model of fire severity, designed from the analysis of field observations, reproduces the effect of local topography (landform category, the slope angle and aspect and flow accumulation), weather conditions (drought index, soil moisture) and fire characteristics (day of year and size of the fire) on the reduction of the organic layer caused by fire. The integration of the fire severity model into an ecosystem process-based model allowed us to document the relative importance and interactions among local topography, fire regime and climate warming on active layer and soil carbon dynamics. Lowlands were more resistant to severe fires and climate warming, showing smaller increases in active layer thickness and soil carbon loss compared to drier flat uplands and slopes. In simulations that included the effects of both warming and fire at the regional scale, fire was primarily responsible for a reduction in organic layer thickness of 0.06 m on average by 2100 that led to an increase in active layer thickness of 1.1 m on average by 2100. The combination of warming and fire led to a simulated cumulative loss of 9.6 kgC m−2 on average by 2100. Our analysis suggests that ecosystem carbon storage in boreal forests in interior Alaska is particularly vulnerable, primarily due to the combustion of organic layer thickness in fire and the related increase in active layer thickness that exposes previously protected permafrost soil carbon to decomposition.

The Effect of Three Different Absorption Cross-Sections and their Temperature Dependence on Total Ozone Measured by a Mid-Latitude Brewer Spectrophotometer

The influence of variations in atmospheric temperature and ozone profiles on the total ozone column (TOC) derived from a Brewer MKII spectrophotometer operating in Thessaloniki, Greece, is investigated using three different sets of ozone absorption cross-sections. The standard Brewer total ozone retrieval algorithm uses the Bass and Paur (1985) cross-sections without accounting for the temperature dependence of the ozone cross-sections which produces a seasonally dependent bias in the measured TOC. The magnitude of this temperature effect depends on the altitude where the bulk of the ozone absorption occurs. Radiosonde measurements for the period 2000 to 2010 combined with climatological ozone profiles were used to calculate the effective temperature of ozone absorption and investigate its effect on the retrieved ozone column. Three different ozone absorption cross-section spectra convolved with the instrument's slit function were used: those of Bass and Paur (hereafter BP), currently used in the standard Brewer retrieval algorithm; those of Brion, Daumont, and Malicet (Malicet et al., 1985; hereafter BDM); and the recently published set by Serdyuchenko et al. (2013 hereafter S13). The temperature dependence of the differential ozone absorption coefficient ranges between 0.09 and 0.13% per degree Celsius for BP, between −0.11 and −0.06% per degree Celsius for BDM, and between 0.018 to 0.022% per degree Celsius for S13, resulting in a seasonal bias in the derived TOC of up to 2%, 1.8%, and 0.4%, respectively. The temperature sensitivity of the differential ozone absorption coefficient for the Brewer spectrophotometer at Thessaloniki for the BP and BDM cross-sections is found to be within the range reported for other Brewer instruments in earlier studies, whereas the seasonal bias in TOC is minimized when using the new S13 cross-sections because of their small temperature dependence.

Warming and glacier recession in the Rakaia valley, Southern Alps of New Zealand, during Heinrich Stadial 1

The termination of the last ice age featured a major reconfiguration of Earthʼs climate and cryosphere, yet the underlying causes of these massive changes continue to be debated. Documenting the spatial and temporal variations of atmospheric temperature during deglaciation can help discriminate among potential drivers. Here, we present a 10Be surface-exposure chronology and glaciological reconstruction of ice recession following the Last Glacial Maximum (LGM) in the Rakaia valley, Southern Alps of New Zealand. Innermost LGM moraines at Big Ben have an age of 17,840 ± 240 yrs, whereas ice-marginal moraines or ice-molded bedrock surfaces at distances up-valley from Big Ben of 12.5 km (Lake Coleridge), ∼25 km (Castle Hill), ∼28 km (Double Hill), ∼43 km (Prospect Hill), and ∼58 km (Reischek knob) have ages of 17,020 ± 70 yrs, 17,100 ± 110 yrs, 16,960 ± 370 yrs, 16,250 ± 340 yrs, and 15,660 ± 160 yrs, respectively. These results indicate extensive recession of the Rakaia glacier, which we attribute primarily to the effects of climatic warming. In conjunction with geomorphological maps and a glaciological reconstruction for the Rakaia valley, we use our chronology to infer timing and magnitude of past atmospheric temperature changes. Compared to an overall temperature rise of ∼4.65 °C between the end of the LGM and the start of the Holocene, the glacier recession between ∼17,840 and ∼15,660 yrs ago is attributable to a net temperature increase of ∼4.0 °C (from −6.25 to −2.25 °C), accounting for ∼86% of the overall warming. Approximately 3.75 °C (∼70%) of the warming occurred between ∼17,840 and ∼16,250 yrs ago, with a further 0.75 °C (∼16%) increase between ∼16,250 and ∼15,660 yrs ago. A sustained southward shift of the Subtropical Front (STF) south of Australia between ∼17,800 and ∼16,000 yrs ago coincides with the warming over the Rakaia valley, and suggests a close link between Southern Ocean frontal boundary positions and southern mid-latitude climate. Most of the deglacial warming in the Southern Alps occurred during the early part of Heinrich Stadial 1 (HS1) of the North Atlantic region. Because the STF is associated with the position of the westerly wind belt, our findings support the concept that a southward shift of Earthʼs wind belts accompanied the early part of HS1 cooling in the North Atlantic, leading to warming and deglaciation in southern middle latitudes.

Lower ionosphere monitoring by the South America VLF Network (SAVNET): C region occurrence and atmospheric temperature variability

AbstractDaily profiles of phase measurements as observed on fixed VLF paths generally show a transient phase advance, followed by a phase delay, for about 90 min after sunrise hours. This is indicative of a reflecting ionospheric C region developing along the terminator line at an altitude below the normal D region. The suggested occurrence of a C region is consistent with rocket measurements made in the 1960s, showing a maximum of the electron density between 64 and 68 km, and by radio sounding in the 1980s. In order to correctly describe the properties of the phase effect associated with the presence of a C region, it is important to understand the subionospheric propagation characteristics of the VLF paths. In this paper, we analyze the variations presented by the temporal properties of the VLF narrowband phase effect and determined a parameter associated with the appearance of the C region at sunrise hours observed by receivers from the South America VLF Network. Periodic patterns emerge from the parameter curves. Two distinct temporal behavior regimes can be identified: one exhibiting slow variations between March and October, and another one exhibiting faster variations between October and March. Solar illumination conditions and the geometrical configuration of the VLF paths relative to the sunrise terminator partly explain the slow variation regime. During periods of faster variations, we have observed good association with atmospheric temperature variability found in the measurements of the Thermosphere Ionosphere Mesosphere Energetics and Dynamics and Sounding of the Atmosphere using Broadband Emission Radiometry satellite instrument, which we assume to be related to the winter anomaly atmospheric phenomenon. However, when comparing the parameter time series with temperature curves, no direct one‐to‐one correspondence was found for transient events.

Seasonal thermoelastic strain and postseismic effects in Parkfield borehole dilatometers

Strainmeter records in three 176–323 m deep boreholes near Parkfield, CA, are dominated by seasonal fluctuations. We show that a significant part of the seasonal data may result from thermoelastic strain induced by atmospheric temperature variations. We test this hypothesis by computing thermoelastic strain in an elastic half-space covered by a thin unconsolidated layer from atmospheric temperature and comparing the results to the borehole strain records. The strain at depth is produced by the temperature field at the bottom of the unconsolidated layer. The model provides reasonable fits to the amplitudes and phases of the seasonal borehole signals. The two key model parameters, thickness of the unconsolidated layer (∼0.3–1.2 m at the used sites) and wavelength of the temperature field (3 km), are sufficiently plausible to support the physical validity of the model. Two instances with persistent deviations between the trends of the predicted thermoelastic strain and observed records may reflect shallow postseismic effects of M⩾4 nearby earthquakes.

Reciprocity-Enhanced Optical Communication Through Atmospheric Turbulence—Part II: Communication Architectures and Performance

Free-space optical (FSO) communication provides rapidly deployable, dynamic communication links that are capable of very high data rates compared with those of radio-frequency systems. As such, FSO communication is ideal for mobile platforms, for platforms that require the additional security afforded by the narrow divergence of a laser beam, and for systems that must be deployed in a relatively short time frame. In clear-weather conditions the data rate and utility of FSO communication links are primarily limited by fading caused by microscale atmospheric temperature variations that create parts-permillion refractive-index fluctuations known as atmospheric turbulence. Typical communication techniques to overcome turbulence-induced fading, such as interleavers with sophisticated codes, lose viability as the data rate is driven higher or the delay tolerance is driven lower. This paper, along with its companion [J. Opt. Commun. Netw. 4, 947 (2012)], present communication systems and techniques that exploit atmospheric reciprocity to overcome turbulence that are viable for high data rate and low delay tolerance systems. Part I proves that reciprocity is exhibited under rather general conditions and derives the optimal power-transfer phase compensation for far-field operation. Part II presents capacity-achieving architectures that exploit reciprocity to overcome the complexity and delay issues that limit state-of-the-art FSO communications.

Solar diurnal anisotropy measured using muons in GRAPES-3 experiment in 2006

The GRAPES-3 experiment at Ooty contains a large-area (560 m2) tracking muon detector. This detector consists of 16 modules, each 35 m2 in area, that are grouped into four supermodules of 140 m2 each. The threshold energy of muons is sec(θ) GeV along a direction with zenith angle θ and the angular resolution of the muon detector is 6°. Typically, it records ~4×109 muons every day. The muon detector has been operating uninterruptedly since 2001, thus providing a high statistics record of the cosmic ray flux as a function of time over one decade. However, prior to using these data, the muon rate has to be corrected for two important atmospheric effects, namely, variations in atmospheric pressure and temperature. Because of the near equatorial location of Ooty (11.4°N), the seasonal variations in the atmospheric temperature are relatively small and shall be ignored here. Due to proximity to the equator, the pressure changes at Ooty display a dominant 12 h periodic behaviour in addition to other seasonal changes. Here, we discuss various aspects of a novel method for accurate pressure measurement and subsequent corrections applied to the GRAPES-3 muon data to correct these pressure-induced variations. The pressure-corrected muon data are used to measure the profile of the solar diurnal anisotropy during 2006. The data, when divided into four segments, display significant variation both in the amplitude (~45%) and phase (~42 m) of the solar diurnal anisotropy during 2006, which was a period of relatively low solar activity.

Low-Level Stability during Winter Storms in the Uinta Basin of Utah: Potential Impacts on Ground-Based Cloud Seeding

Low-level thermodynamic stability, an important consideration for winter season ground-based cloud seeding site selection and conduct of operations, varies considerably in and near mountainous terrain. Rawinsonde observations may sometimes be poorly representative of nearby areas, with significant lower-level atmospheric temperature variability common between basins and sometimes within a basin. Operational forecast models may lack the ability to resolve or properly initialize low-level stability or “cold pooling” specific to a given basin or portion of a basin. Analyses of surface observations, as well as plume dispersion modeling with HYSPLIT, can be used both for real-time operations and in post-hoc examinations of low-level stability specific to storm periods with cloud seeding potential. Analyses of this type have been performed in various portions of Utah, and a recent analysis in the Uinta Range and Uinta Basin area of northeastern Utah highlights both the geographic variability and the seasonality of basin cold pooling. The Uinta Basin analyses have shown much greater low-level thermodynamic stability during relevant winter storm periods than other portions of Utah. Strong correlation of stability to site elevation within the basin, as well as distinct seasonality, are observed.

Radiometric comparison of Mars Climate Sounder and Thermal Emission spectrometer measurements

Mars Climate Sounder (MCS) nadir oriented thermal infrared and solar channel measurements are compared with Thermal Emission Spectrometer (TES) measurements across multiple Mars years. Thermal infrared measurements were compared by convolving the TES data using the MCS spectral band passes. The MCS solar channel measurements were calibrated using Compact Reconnaissance Imaging Spectrometer for Mars observations to provide the proper gain factor (3.09×10−3Wsr−1m−2μm−1). The comparisons of the datasets show that day and night surface and atmospheric temperatures are within 3K over the course of 5 martian years, after accounting for the local time differences. Any potential interannual variations in global average temperature are masked by calibration and modeling uncertainties. Previous work attributed apparent interannual global surface and atmospheric temperature variations to major dust storm activity; however, this variation has since been attributed to a calibration error in the TES dataset that has been corrected. MCS derived Lambert albedos are slightly higher than TES measurements acquired over the same season and locations. Most of this difference can be attributed to the spectral response functions of MCS and TES. Consistent with previous work, global albedo is highly variable (∼6%) and this variability must be taken into account when determining long term global trends. Vertical aerosol distributions were also derived from the calibrated MCS visible channel limb measurements, demonstrating the utility of the MCS visible channel data for monitoring of aerosols.