High-resolution Temperature Profiles Research Articles

The tropical tropopause inversion layer: variability and modulation by equatorial waves

Abstract. The tropical tropopause layer (TTL) acts as a transition layer between the troposphere and the stratosphere over several kilometers, where air has both tropospheric and stratospheric properties. Within this region, a fine-scale feature is located: the tropopause inversion layer (TIL), which consists of a sharp temperature inversion at the tropopause and the corresponding high static stability values right above, which theoretically affect the dispersion relations of atmospheric waves like Rossby or inertia–gravity waves and hamper stratosphere–troposphere exchange (STE). Therefore, the TIL receives increasing attention from the scientific community, mainly in the extratropics so far. Our goal is to give a detailed picture of the properties, variability and forcings of the tropical TIL, with special emphasis on small-scale equatorial waves and the quasi-biennial oscillation (QBO).We use high-resolution temperature profiles from the COSMIC satellite mission, i.e., ∼ 2000 measurements per day globally, between 2007 and 2013, to derive TIL properties and to study the fine-scale structures of static stability in the tropics. The situation at near tropopause level is described by the 100 hPa horizontal wind divergence fields, and the vertical structure of the QBO is provided by the equatorial winds at all levels, both from the ERA-Interim reanalysis.We describe a new feature of the equatorial static stability profile: a secondary stability maximum below the zero wind line within the easterly QBO wind regime at about 20–25 km altitude, which is forced by the descending westerly QBO phase and gives a double-TIL-like structure. In the lowermost stratosphere, the TIL is stronger with westerly winds. We provide the first evidence of a relationship between the tropical TIL strength and near-tropopause divergence, with stronger (weaker) TIL with near-tropopause divergent (convergent) flow, a relationship analogous to that of TIL strength with relative vorticity in the extratropics.To elucidate possible enhancing mechanisms of the tropical TIL, we quantify the signature of the different equatorial waves on the vertical structure of static stability in the tropics. All waves show, on average, maximum cold anomalies at the thermal tropopause, warm anomalies above and a net TIL enhancement close to the tropopause. The main drivers are Kelvin, inertia–gravity and Rossby waves. We suggest that a similar wave modulation will exist at mid- and polar latitudes from the extratropical wave modes.

Experimental study of air-cooled water condensation in slightly inclined circular tube using infrared temperature measurement technique

This study presents the results of an investigation of the air-cooled water condensation heat transfer characteristics inside a slightly inclined circular tube made of transparent Pyrex glass. The high-resolution wall temperature data and stratified film formations could be obtained with the assistance of an infrared (IR) thermometry technique and side-view visualization using a CCD camera. In all experimental cases, the condensation flow patterns were in the fully-stratified flow region. In addition, the experimentally measured void fraction corresponded well with the logarithmic mean void fraction model. The local temperature differences in the cooling air flow across the condenser tube and high-resolution temperature profiles on the tube’s outer wall were obtained in the experimental measurements. Under the experimental conditions of this study, the local heat flux distributions in the longitudinal direction of the test tube were strongly dependent on the cooling air velocity. And, with the help of IR thermometry, the tube outer wall temperature data at 45 local points could be measured. From the data, the asymmetry distribution of the local wall temperatures and the accurate location of the transition from two-phase mixture to single phase liquid inside the tube could be obtained. Also, the analysis of the thermal resistances by condensation, wall conduction and air convection showed that the air convective heat transfer behavior can play a dominant role to the local heat transfer characteristics. Finally, in order to obtain the local heat flux distribution along the tube’s outer wall, a two-dimensional computational fluid dynamics analysis was conducted. From this calculation, it was resulted that about 70% of total heat transfer rate from the tube surface was released through the tube region lower than the center point. These results were caused by the distribution of air convective heat transfer coefficient on the tube surface.

Heterogeneous bedrock investigation for a closed-loop geothermal system: A case study

This paper investigates bedrock heterogeneity by applying three different geophysical approaches, in order to study the long-term behaviour and the interaction between closed-loop geothermal systems. The investigated site consists of four boreholes equipped with geothermal pipes on the campus of University of Liege, Belgium. The first approach includes acoustic borehole imaging, gamma-ray logging and cuttings observation and results to a detailed fracture characterisation, rock identification and layer dip angle determination. The second approach consists of measuring the thermal conductivity of cuttings at the laboratory. Study of cuttings thermal conductivity measurements can contribute to bedrock heterogeneity knowledge concerning the transition of one formation to another and the layer dipping. The third approach is based on high-resolution temperature profiles, measured during the hardening of the grouting material and the recovery phase of a Distributed Thermal Response Test. Through this approach a correlation of the temperature profiles to the geological characteristics of the surrounding bedrock is identified. The analysis of this correlation can provide information on fractured zones, alternation of different rock types and layering dipping. This latter approach can be easily applied on closed-loop geothermal systems to characterise the bedrock and investigate its heterogeneity as well as contribute to the their long-term behaviour prediction and to the optimisation of their efficiency.

Stratospheric variability of wave activity and parameters in equatorial coastal and tropical sites during the West African monsoon

Recent numerical studies in stratospheric dynamics and its variability as well as climate, have highlighted the need of more observational analyses to improve simulation of the West African monsoon (WAM). In this paper, activity and spectral characteristics of short-scale vertical waves (wavelengths <4 km) are analysed in equatorial coastal and tropical lower stratosphere during the WAM. A first detailed description of such waves over West Africa is derived from high-resolution vertical profiles of temperature and horizontal wind obtained during Intensive Observation Period of the African Monsoon Multidisciplinary Analyses (AMMA) Campaign 2006. Monthly variation of wave energy density is revealed to trace the progression of the inter-tropical convergence zone (ITCZ) over West Africa. Mesoscale inertia gravity-waves structures with vertical and horizontal wavelengths of 1.5–2.5 and 400–1100 km respectively and intrinsic frequencies of 1.1–2.2 f or periods <2 days are observed in the tropical LS with intense activity during July and August when the WAM is installed over the tropical West Africa. Over equatorial region, gravity waves with intrinsic frequencies of 1.4–4 f or periods <5.2 days, vertical wavelength of 2.1 km and long horizontal wavelengths of 1300 km are intense during the WAM coastal phase. From July to October, gravity waves with intrinsic frequencies of 1.2–3.8 f or periods <6 days, vertical wavelength of 2.1 km and horizontal wavelengths of 1650 km are less intense during the WAM Sahelian phase of the WAM, March–June. Unlike potential energy density, kinetic energy density is observed to be a good proxy for the activity of short-scale vertical waves during the WAM because quasi-inertial waves are dominant. Long-term wave activity variation from January 2001 to December 2009, highlights strong year-to-year variation superimposed on convective activity and quasi-biennial oscillation-like variations especially above tropical stations.

Validation of AIRS version 6 temperature profiles and surface‐based inversions over Antarctica using Concordiasi dropsonde data

AbstractDuring the 2010 Concordiasi field experiment, 635 dropsondes were released from the lower stratosphere providing in situ atmospheric profiles from the release height (~60 hPa) to the surface over Antarctica. They provide a unique data set of high vertical resolution temperature profiles over the entire Antarctic continent and surrounding ocean. This study uses temperature profiles and derived surface‐based inversion (SBI) properties from the sonde data set to evaluate Atmospheric Infrared Sounder (AIRS) versions 5 (v5) and 6 (v6) temperature profiles. A total of 1486 matched pairs of profiles are available for analysis. The AIRS averaging kernel, representing the AIRS measurement sensitivity, is applied to the dropsonde profiles. The AIRS data are compared to kernel‐averaged dropsonde profiles and found, on average, to have a small cold bias (~0.5°C) (for v6) in the troposphere. AIRS v6 is improved over v5 with both profile‐averaged bias and root‐mean‐square errors reduced by over 25%. Compared to the kernel‐averaged dropsonde profiles, AIRS v6 accurately detects the existence of SBIs in 79% of the profiles and agrees on the inversion depth 79% of the time. AIRS correctly identifies SBIs in 59% of cases when compared to the full‐resolution sonde. AIRS systematically underestimates the SBI intensity. This is due to warmer reported AIRS surface air temperatures (Ta) than Ta measured with the dropsonde. Replacement of AIRS Ta with that measured by the dropsonde improves the agreement in both SBI detection and intensity. If AIRS Ta could be improved, AIRS has the potential to be a stand‐alone SBI detection tool over Antarctica.

Global Hawk dropsonde observations of the Arctic atmosphere obtained during the Winter Storms and Pacific Atmospheric Rivers (WISPAR) field campaign

Abstract. In February and March of 2011, the Global Hawk unmanned aircraft system (UAS) was deployed over the Pacific Ocean and the Arctic during the Winter Storms and Pacific Atmospheric Rivers (WISPAR) field campaign. The WISPAR science missions were designed to (1) mprove our understanding of Pacific weather systems and the polar atmosphere; (2) evaluate operational use of unmanned aircraft for investigating these atmospheric events; and (3) demonstrate operational and research applications of a UAS dropsonde system at high latitudes. Dropsondes deployed from the Global Hawk successfully obtained high-resolution profiles of temperature, pressure, humidity, and wind information between the stratosphere and surface. The 35 m wingspan Global Hawk, which can soar for ~ 31 h at altitudes up to ~ 20 km, was remotely operated from NASA's Dryden Flight Research Center at Edwards Air Force Base (AFB) in California. During the 25 h polar flight on 9–10 March 2011, the Global Hawk released 35 sondes between the North Slope of Alaska and 85° N latitude, marking the first UAS Arctic dropsonde mission of its kind. The polar flight transected an unusually cold polar vortex, notable for an associated record-level Arctic ozone loss, and documented polar boundary layer variations over a sizable ocean–ice lead feature. Comparison of dropsonde observations with atmospheric reanalyses reveal that, for this day, large-scale structures such as the polar vortex and air masses are captured by the reanalyses, while smaller-scale features, including low-level jets and inversion depths, are mischaracterized. The successful Arctic dropsonde deployment demonstrates the capability of the Global Hawk to conduct operations in harsh, remote regions. The limited comparison with other measurements and reanalyses highlights the potential value of Arctic atmospheric dropsonde observations where routine in situ measurements are practically nonexistent.

A new method for the validation of the GOMOS high resolution temperature profiles products

&lt;p&gt;This article proposes a new validation method for GOMOS HRTP atmospheric temperature and density profiles, with the aim of detecting and removing 0.2 to 5 km scale vertical structures in order to minimise the impact of atmospheric artefacts in the comparison exercises. The proposed approach is based on the use of the “Morlet” Continuous Wavelet Transformation (CWT), for the characterisation and removal of non-stationary and localised vertical structures, in order to produce wave-free profiles of atmospheric temperature and density. Comparison of wave-free temperature/density profiles and wavy structures profiles with those estimated from a limited number of collocated SHADOZ soundings for the years of 2003, 2004 and 2008, is discussed in detail. First results suggest that the proposed approach could lead to a significantly improved HRTP validation scheme, in terms of reduced uncertainties in the estimated biases. Furthermore, this method may be adopted for the study of the vertical component of gravity waves from high spatial/temporal resolution data.&lt;/p&gt;

A Neural Network Approach to Improve the Vertical Resolution of Atmospheric Temperature Profiles From Geostationary Satellites

Tropospheric temperature measurements at high temporal, spatial, and vertical resolutions are required for many meteorological studies. Radiosonde and Global Positioning System radio occultation (GPSRO) observations have very high vertical resolutions but poor in spatial and temporal coverage. Although the sounders on geostationary satellites can provide high temporal and spatial resolutions, their vertical resolution is poor. In this letter, we proposed a method to increase the vertical resolution of tropospheric temperature profiles obtained from geostationary satellite observations based on an artificial neural network (ANN) approach so that high-resolution temperature profiles are available in all four dimensions. We simulated the pressure levels of the forthcoming Indian National Satellite System (INSAT) 3-D temperature measurements from 950 to 100 hPa using 1-D variational temperature profiles of the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC). We used these low-resolution simulated profiles as the predictors and the high-resolution GPSRO COSMIC profiles as predictants. The data during 2007 and 2008 were used to develop the model, and the data during 2009 were used for validation. The correlation coefficient of greater than 0.94 is observed throughout the pressure levels for all the three data sets. The root-mean-square differences of training, selection, and validation sets are 0.43, 0.46, and 0.51, respectively. A scatter index of less than 0.002 for all the three data sets indicates the accuracy of the estimations.

Fine-Scale Characteristics of Temperature, Wind, and Turbulence in the Lower Atmosphere (0–1,300 m) Over the South Peruvian Coast

We report results of preliminary high-resolution in situ atmospheric measurements through the boundary layer and lower atmosphere over the southern coast of Perú. This region of the coast is of particular interest because it lies adjacent to the northern coastal edge of the sub-tropical south-eastern Pacific, a very large area of ocean having a persistent stratus deck located just below the marine boundary layer (MBL) inversion. Typically, the boundary layer in this region during winter is topped by a quasi-permanent, well-defined, and very large temperature gradient. The data presented herein examine fine-scale details of the coastal atmosphere at a point where the edge of this MBL extends over the coastline as a result of persistent onshore flow. Atmospheric data were gathered using a recently-developed in-house constructed, GPS-controlled, micro-autonomous-vehicle aircraft (the DataHawk). Measured quantities include high-resolution profiles of temperature, wind, and turbulence structure from the surface to 1,300 m.

Tropical Cold-Point Tropopause: Climatology, Seasonal Cycle, and Intraseasonal Variability Derived from COSMIC GPS Radio Occultation Measurements

Abstract The finescale structure of the tropical cold-point tropopause (CPT) is examined using high-resolution temperature profiles derived from Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) global positioning system (GPS) radio occultation measurements for 4 yr from September 2006 to August 2010. The climatology, seasonal cycle, and intraseasonal variability are analyzed for three CPT properties: temperature (T-CPT), pressure (P-CPT), and sharpness (S-CPT). Their relationships with tropospheric and stratospheric processes are also discussed. The climatological P-CPT is largely homogeneous in the deep tropics, whereas T-CPT and S-CPT exhibit local minima and maxima, respectively, at the equator in the vicinity of deep convection regions. All three CPT properties, however, show coherent seasonal cycle in the tropics; the CPT is colder, higher (lower in pressure), and sharper during boreal winter than during boreal summer. This seasonality is consistent with the seasonal cycle of tropical upwelling, which is largely driven by stratospheric and near-tropopause processes, although the amplitude of the seasonal cycle of T-CPT and S-CPT is modulated by tropospheric circulations. On intraseasonal time scales, P-CPT and T-CPT exhibit homogeneous variability in the deep tropics, whereas S-CPT shows pronounced local variability and seasonality. The wavenumber–frequency spectra reveal that intraseasonal variability of CPT properties is primarily controlled by Kelvin waves, with a nonnegligible contribution by Madden–Julian oscillation convection. The Kelvin waves, which are excited by deep convection but often propagate along the equator freely, explain the homogeneous P-CPT and T-CPT variabilities. On the other hand, the vertically tilted dipole of temperature anomalies, which is associated with convectively coupled equatorial waves, determines the local structure and seasonality of S-CPT variability.

Investigating riparian groundwater flow close to a losing river using diurnal temperature oscillations at high vertical resolution

Abstract. River-water infiltration is of high relevance for hyporheic and riparian groundwater ecology as well as for drinking water supply by river-bank filtration. Heat has become a popular natural tracer to estimate exchange rates between rivers and groundwater. However, quantifying flow patterns and velocities is impeded by spatial and temporal variations of exchange fluxes, insufficient sensors spacing during field investigations, or simplifying assumptions for analysis or modeling such as uniform flow. The objective of this study is to investigate lateral shallow groundwater flow upon river-water infiltration at the shoreline of the riverbed and in the adjacent riparian zone of the River Thur in northeast Switzerland. Here we have applied distributed temperature sensing (DTS) along optical fibers wrapped around tubes to measure high-resolution vertical temperature profiles of the unsaturated zone and shallow riparian groundwater. Diurnal temperature oscillations were tracked in the subsurface and analyzed by means of dynamic harmonic regression to extract amplitudes and phase angles. Subsequent calculations of amplitude attenuation and time shift relative to the river signal show in detail vertical and temporal variations of heat transport in shallow riparian groundwater. In addition, we apply a numerical two-dimensional heat transport model for the unsaturated zone and shallow groundwater to obtain a better understanding of the observed heat transport processes in shallow riparian groundwater and to estimate the groundwater flow velocity. Our results show that the observed riparian groundwater temperature distribution cannot be described by uniform flow, but rather by horizontal groundwater flow velocities varying over depth. In addition, heat transfer of diurnal temperature oscillations from the losing river through shallow groundwater is influenced by thermal exchange with the unsaturated zone. Neglecting the influence of the unsaturated zone would cause biased interpretation and underestimation of groundwater flow velocities. The combination of high resolution field data and modeling shows the complex hydraulic and thermal processes occurring in shallow riparian groundwater close to losing river sections as well as potential errors sources for interpreting diurnal temperature oscillations in such environments.

Mooring-Based Observations of Double-Diffusive Staircases over the Laptev Sea Slope*

AbstractA yearlong time series from mooring-based high-resolution profiles of water temperature and salinity from the Laptev Sea slope (2003–04; 2686-m depth; 78°26′N, 125°37′E) shows six remarkably persistent staircase layers in the depth range of ~140–350 m encompassing the upper Atlantic Water (AW) and lower halocline. Despite frequent displacement of isopycnal surfaces by internal waves and eddies and two strong AW warming pulses that passed through the mooring location in February and late August 2004, the layers preserved their properties. Using laboratory-derived flux laws for diffusive convection, the authors estimate the time-averaged diapycnal heat fluxes across the four shallower layers overlying the AW core to be ~8 W m−2. Temporal variability of these fluxes is strong, with standard deviations of ~3–7 W m−2. These fluxes provide a means for effective transfer of AW heat upward over more than a 100-m depth range toward the upper halocline. These findings suggest that double diffusion is an important mechanism influencing the oceanic heat fluxes that help determine the state of Arctic sea ice.

東京湾における貧酸素水塊と鉛直混合強度に関する現地観測

We describe relationships between dissolved oxygen (DO) and vertical mixing rate (Kz) based on in-situ survey data in Tokyo Bay. Seven field observations were carried out in the period, July 2011- March 2012, using the micro-structure profiler to simultaneously measure high-resolution profiles of shear, temperature, salinity, fluorescence and DO. The observed data showed that hypoxic water mass occurred in the middle layer at the end of August. The hypoxic water was located in the region with Kz ‹ 10-5 m2/s, which was distributed between the surface mixing layer and the bottom boundary. The profile data also indicated that the intrusion of the bottom high-salinity water from the bay mouth to the bay head was an important role in the recovery process of DO in Tokyo Bay.

The Turbopause experiment: atmospheric stability and turbulent structure spanning the turbopause altitude

Abstract. Very few sequences of high resolution wind and temperature measurements in the lower thermosphere are available in the literature, which makes it difficult to verify the simulation results of models that would provide better understanding of the complex dynamics of the region. To address this problem the Turbopause experiment used four rockets launched over a period of approximately two hours from Poker Flat Research Range, Alaska (64° N, 147° W) on the night of 17–18 February 2009. All four rocket payloads released trimethyl aluminum trails for neutral wind and turbulence measurements, and two of the rockets carried ionization gauges and fixed-bias Langmuir probes measuring neutral and electron densities, small-scale fluctuations and neutral temperatures. Two lidars monitored temperature structure and sodium densities. The observations were made under quiet geomagnetic conditions and show persistence in the wind magnitudes and shears throughout the observing period while being modulated by inertia-gravity waves. High resolution temperature profiles show the winter polar mesosphere and lower thermosphere in a state of relatively low stability with several quasi-adiabatic layers between 74 and 103 km. Temperature and wind data were combined to calculate Richardson number profiles. Evidence for turbulence comes from simultaneous observations of density fluctuations and downward transport of sodium in a mixed layer near 75 km; the observation of turbulent fluctuations and energy dissipation from 87–90 km; and fast and irregular trail expansion at 90–93 km, and especially between 95 to 103 km. The regions of turbulent trails agree well with regions of quasi-adiabatic temperature gradients. Above 103 km, trail diffusion was mainly laminar; however, unusual features and vortices in the trail diffusion were observed up to 118 km that have not been as prevalent or as clearly evident in earlier trail releases.

Modeling time series of microwave brightness temperature at Dome C, Antarctica, using vertically resolved snow temperature and microstructure measurements

AbstractTime series of observed microwave brightness temperatures at Dome C, East Antarctic plateau, were modeled over 27 months with a multilayer microwave emission model based on dense-medium radiative transfer theory. The modeled time series of brightness temperature at 18.7 and 36.5 GHz were compared with Advanced Microwave Scanning Radiometer–EOS observations. The model uses in situ high-resolution vertical profiles of temperature, snow density and grain size. The snow grain-size profile was derived from near-infrared (NIR) reflectance photography of a snow pit wall in the range 850–1100 nm. To establish the snow grain-size profile, from the NIR reflectance and the specific surface area of snow, two empirical relationships and a theoretical relationship were considered. In all cases, the modeled brightness temperatures were overestimated, and the grain-size profile had to be scaled to increase the scattering by snow grains. Using a scaling factor and a constant snow grain size below 3 m depth (i.e. below the image-derived snow pit grain-size profile), brightness temperatures were explained with a root-mean-square error close to 1 K. Most of this error is due to an overestimation of the predicted brightness temperature in summer at 36.5 GHz.

Retrieval of atmospheric parameters from GOMOS data

Abstract. The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on board the European Space Agency's ENVISAT satellite measures attenuation of stellar light in occultation geometry. Daytime measurements also record scattered solar light from the atmosphere. The wavelength regions are the ultraviolet-visible band 248–690 nm and two infrared bands at 755–774 nm and at 926–954 nm. From UV-Visible and IR spectra the vertical profiles of O3, NO2, NO3, H2O, O2 and aerosols can be retrieved. In addition there are two 1 kHz photometers at blue 473–527 nm and red 646–698 nm. Photometer data are used to correct spectrometer measurements for scintillations and to retrieve high resolution temperature profiles as well as gravity wave and turbulence parameters. Measurements cover altitude region 5–150 km. Atmospherically valid data are obtained in 15–100 km. In this paper we present an overview of the GOMOS retrieval algorithms for stellar occultation measurements. The low signal-to-noise ratio and the refractive effects due to the point source nature of stars have been important drivers in the development of GOMOS retrieval algorithms. We present first the Level 1b algorithms that are used to correct instrument related disturbances in the spectrometer and photometer measurements The Level 2 algorithms deal with the retrieval of vertical profiles of atmospheric gaseous constituents, aerosols and high resolution temperature. We divide the presentation into correction for refractive effects, high resolution temperature retrieval and spectral/vertical inversion. The paper also includes discussion about the GOMOS algorithm development, expected improvements, access to GOMOS data and alternative retrieval approaches.

Global estimates of gravity wave parameters from GPS radio occultation temperature data

Gravity waves (GWs) play critical roles in the global circulation and the temperature and constituent structures in the middle atmosphere. They also play significant roles in the dynamics and transport and mixing processes in the upper troposphere and lower stratosphere and can affect tropospheric weather. Despite significant advances in our understanding of GWS and their effects in different regions of the atmosphere in the past few decades, observational constraints on GW parameters including momentum flux and propagation direction are still sorely lacking. Global Positioning System (GPS) radio occultation (RO) technique provides global, all‐weather, high vertical resolution temperature profiles in the stratosphere and troposphere. The unprecedentedly large number of combined temperature soundings from the Constellation Observing System for Meteorology, Ionosphere, and Climate and Challenging Minisatellite Payload GPS RO missions allows us to obtain GW perturbations by removing the gravest zonal modes using the wavelet method for each day. We extended the GW analysis method of Alexander et al. (2008) to three dimensions to estimate the complete set of GW parameters (including momentum flux and horizontal propagation direction) from the GW temperature perturbations thus derived. To demonstrate the effectiveness of the analysis, we showed global estimates of GW temperature amplitudes, vertical and horizontal wavelengths, intrinsic frequency, and vertical flux of horizontal momentum in the altitude range of 17.5–22.5 km during December 2006 to February 2007. Consistent with many previous studies, GW temperature amplitudes are a maximum in the tropics and are generally larger over land, likely reflecting convection and topography as main GW sources. GW vertical wavelengths are a minimum at equator, likely due to wave refraction, whereas GW horizontal wavelengths are generally longer in the tropics. Most of the waves captured in the analysis of the GPS data are low‐intrinsic frequency inertia‐GWs, and the estimated intrinsic frequencies scaled by the Coriolis parameter also show a strong maximum at equator. Enhanced wave fluxes are linked to convection, topography, and storm tracks, among others. As preliminary tests of the analysis in deriving horizontal propagation directions, we compared the GPS estimates with the corresponding estimates from the U.S. high vertical resolution radiosonde data using the conventional Stokes parameters method and we also conducted a separate analysis of the GPS data over the southern Andes in South America. We also showed the first global estimates of GW propagation directions from the GPS data. Finally, the sensitivity of the analysis to the temporal and spatial dimensions of the longitude × latitude × time cells and the uncertainties of the analysis and possible ways to reduce these uncertainties are discussed.

Improved Resolution of Ambient Flow through Fractured Rock with Temperature Logs

In contaminant hydrogeology, investigations at fractured rock sites are typically undertaken to improve understanding of the fracture networks and associated groundwater flow that govern past and/or future contaminant transport. Conventional hydrogeologic, geophysical, and hydrophysical techniques used to develop a conceptual model are often implemented in open boreholes under conditions of cross-connected flow. A new approach using high-resolution temperature (+/-0.001 degrees C) profiles measured within static water columns of boreholes sealed using continuous, water-inflated, flexible liners (FLUTe) identifies hydraulically active fractures under ambient (natural) groundwater flow conditions. The value of this approach is assessed by comparisons of temperature profiles from holes (100 to 200 m deep) with and without liners at four contaminated sites with distinctly different hydrogeologic conditions. The results from the lined holes consistently show many more hydraulically active fractures than the open-hole profiles, in which the influence of vertical flow through the borehole between a few fractures masks important intermediary flow zones. Temperature measurements in temporarily sealed boreholes not only improve the sensitivity and accuracy of identifying hydraulically active fractures under ambient conditions but also offer new insights regarding previously unresolvable flow distributions in fractured rock systems, while leaving the borehole available for other forms of testing and monitoring device installation.

A comparative and numerical study of effects of gravity waves in small miss-distance and miss-time GPS radio occultation temperature profiles

The Global Positioning System (GPS) Radio Occultation (RO) technique has global coverage and is capable of generating high vertical resolution temperature profiles of the upper troposphere and lower stratosphere with sub-Kelvin accuracy and long-term stability, regardless of weather conditions. In this work, we take advantage of the anomalously high density of occultation events at the eastern side of the highest Andes Mountains during the initial mission months of COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate). This region is well-known for its high wave activity. We choose to study two pairs of GPS RO, both containing two occultations that occurred close in time and space. One pair shows significant differences between both temperature profiles. Numerical simulations with a mesoscale model were performed, in order to understand this discrepancy. It is attributed to the presence of a horizontal inhomogeneous structure caused by gravity waves.

Neutral Saturated Lapse Rate: An Experimental Check from CALJET-1998 and PACJET-2001

Abstract The lapse rates of high-resolution temperature profiles during nearly neutral, saturated conditions are compared with the saturated adiabatic lapse rate and with that proposed by Richiardone and Giusti. A good agreement between the latter and the mean value of the observed lapse rate is found, whereas the saturated adiabatic lapse rate differs significantly, confirming experimentally that it is not completely correct to assess the moist neutrality from a comparison with the saturated adiabatic lapse rate. The lapse-rate distribution supports the hypothesis that the lapse-rate statistics is a local collection of saturated adiabatic lapse rates in a background normal distribution centered around the neutrality.