scholarly journals Performance of the Vaisala RS80A/H and RS90 Humicap Sensors and the Meteolabor “Snow White” Chilled-Mirror Hygrometer in Paramaribo, Suriname

2006 ◽  
Vol 23 (11) ◽  
pp. 1506-1518 ◽  
Author(s):  
Gé Verver ◽  
Masatomo Fujiwara ◽  
Pier Dolmans ◽  
Cor Becker ◽  
Paul Fortuin ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Time Lag ◽  
Lower Troposphere ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Snow White ◽  
Study Results ◽  
The Tropics ◽  
Humidity Profiles ◽  
Dry Bias

Abstract In climate research there is a strong need for accurate observations of water vapor in the upper atmosphere. Radiosoundings provide relative humidity profiles but the accuracy of many routine instruments is notoriously inadequate in the cold upper troposphere. In this study results from a soundings program executed in Paramaribo, Suriname (5.8°N, 55.2°W), are presented. The aim of this program was to compare the performance of different humidity sensors in the upper troposphere in the Tropics and to test different bias corrections suggested in the literature. The payload of each sounding consisted of a chilled-mirror “Snow White” sensor from Meteolabor AG, which was used as a reference, and two additional sensors from Vaisala, that is, either the RS80A, the RS80H, or the RS90. In total 37 separate soundings were made. For the RS80A a clear, dry bias of between −4% and −8% RH is found in the lower troposphere compared to the Snow White observation, confirming the findings in previous studies. A mean dry bias was found in the upper troposphere, which could be effectively corrected. The RS80H sensor shows a significant wet bias of 2%–5% in RH in the middle and upper troposphere, which has not been reported before. Comparing observations with RS80H sensors of different ages gives no indication of sensor aging or sensor contamination. It is therefore concluded that the plastic cover introduced by Vaisala to avoid sensor contamination is effective. Finally, the RS90 sensor yields a small but significant wet bias of 2%–3% below 7-km altitude. The time-lag error correction from Miloshevich et al. was applied to the Vaisala data, which resulted in an increased variability in the relative humidity profile above 9- (RS80A), 8- (RS80H), and 11-km (RS90) altitude, respectively, which is in better agreement with the Snow White data. The averaged Snow White profile is compared with the average profiles of relative humidity from the European Centre for Medium-Range Weather Forecasts (ECMWF). No significant bias is found in either the analyses or the forecasts. The correlation coefficient for the Snow White and ECMWF data between 200 and 800 hPa was 0.66 for the 36-h forecast and 0.77 for the analysis.

scholarly journals Tropospheric Comparisons of Vaisala Radiosondes and Balloon-Borne Frost-Point and Lyman-α Hygrometers during the LAUTLOS-WAVVAP Experiment

2008 ◽  
Vol 25 (2) ◽  
pp. 149-166 ◽  
Author(s):  
T. M. Suortti ◽  
R. Kivi ◽  
A. Kats ◽  
V. Yushkov ◽  
N. Kämpfer ◽  
...  
Keyword(s):  
Radiation Effects ◽  
Time Lag ◽  
Lower Troposphere ◽  
The Other ◽  
Large Temperature ◽  
Upper Troposphere ◽  
Lag Effects ◽  
Frost Point ◽  
Snow White ◽  
Dry Bias

Abstract The accuracy of all types of Vaisala radiosondes and two types of Snow White chilled-mirror hygrosondes was assessed in an intensive in situ comparison with reference hygrometers. Fourteen nighttime reference comparisons were performed to determine a working reference for the radiosonde comparisons. These showed that the night version of the Snow White agreed best with the references [i.e., the NOAA frost-point hygrometer (FPH) and University of Colorado cryogenic frost-point hygrometer (CFH)], but that the daytime version had severe problems with contamination in the humid upper troposphere. Since the RS92 performance was superior to the other radiosondes and to the day version of the Snow White, it was selected to be the working reference. According to the reference comparison, the RS92 has no bias in the mid- and lower troposphere, with deviations <±5% in relative humidity (RH). In the upper troposphere, the RS92 has a ∼5% RH wet bias, which is partly due to the RS92 time lag error and the termination of the heating cycle. It was shown that the time lag effects relating to Vaisala radiosondes can be corrected. Because these were nighttime comparisons, they can be considered to be free from solar radiation effects. Neither the radiosondes nor the Snow White succeeded in reproducing reference class hygrometer profiles in the stratosphere. According to the 29 radiosonde intercomparisons, the RS92 and the modified RS90 (FN) had the best mutual agreement and no bias. The disagreement is largest (<±10% RH) at low temperatures (T ≪ −30°C), where the FN underestimated (overestimated) in high (low) ambient RH. In comparison with the RS92, the RS90 had a semilinearly increasing wet bias with decreasing temperature, where the bias was ∼10% RH at −60°C. The RS80-A suffers from a large temperature-dependent dry bias in high RH conditions, being over 30% RH at −60°C and ∼5% RH near 0°C. The RS80-A dry bias can be almost totally removed with the correction algorithm by Leiterer et al., which was chosen as the best available. The other approach tested tends to overcorrect in high RH conditions when T < −50°C. For T > −30°C it is ineffective and does not correct the RS80-A dry bias in high ambient RH.

scholarly journals Water vapour and ozone profiles in the midlatitude upper troposphere

2004 ◽  
Vol 4 (6) ◽  
pp. 8357-8379 ◽  
Author(s):  
G. Vaughan ◽  
C. Cambridge ◽  
L. Dean ◽  
A. W. Phillips
Keyword(s):  
Relative Humidity ◽  
Uniform Distribution ◽  
Water Vapour ◽  
Humidity Sensors ◽  
Upper Troposphere ◽  
Peltier Cooling ◽  
Snow White ◽  
Mirror Reflectivity ◽  
Upper Tropospheric Humidity ◽  
Humidity Profiles

Abstract. We present an investigation of upper tropospheric humidity profiles measured with a standard radiosonde, the Vaisala RS80-A, and a commercial frost-point hygrometer, the Snow White. Modifications to the Snow White, to enable the mirror reflectivity and Peltier cooling current to be monitored during flight, were found to be necessary to determine when the instrument was functioning correctly; a further modification to prevent hydrometeors entering the inlet was also implemented. From 23 combined flights of an ozonesonde, radiosonde and Snow White between September 2001 and July 2002, clear agreement was found between the two humidity sensors, with a mean difference of <2% in relative humidity from 2 to 10 km, and 2.2% between 10 and 13 km. This agreement required a correction to the radiosonde humidity, as described by Miloshevich et al. (2001). Using this result, the dataset of 324 ozonesonde/RS80-A profiles measured from Aberystwyth between 1991 and 2002 was examined to derive statistics for the distribution of water vapour and ozone. Supersaturation with respect to ice was frequently seen at the higher levels – 24% of the time in winter between 8 and 10 km. The fairly uniform distribution of relative humidity persisted to 120% in winter, but decreased rapidly above 100% in summer.

scholarly journals MIPAS reduced spectral resolution UTLS-1 mode measurements of temperature, O<sub>3</sub>, HNO<sub>3</sub>, N<sub>2</sub>O, H<sub>2</sub>O and relative humidity over ice: retrievals and comparison to MLS

2009 ◽  
Vol 2 (1) ◽  
pp. 439-487 ◽  
Author(s):  
S. Chauhan ◽  
M. Höpfner ◽  
G. P. Stiller ◽  
T. von Clarmann ◽  
B. Funke ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Pressure Range ◽  
Michelson Interferometer ◽  
Analysis Data ◽  
Height Range ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Mixing Ratios ◽  
Medium Range ◽  
The Tropics

Abstract. During several periods since 2005 the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat has performed observations dedicated to the region of the upper troposphere/lower stratosphere (UTLS). For the duration of November/December 2005 global distributions of temperature and several trace gases from MIPAS UTLS-1 mode measurements have been retrieved using the IMK/IAA (Institut für Meteorologie und Klimaforschung/Instituto de Astrofísica de Andalucía) scientific processor. In the UTLS region a vertical resolution of 2.5 to 3 km has been achieved. The retrieved temperature, H2O, O3, HNO3, N2O, and relative humidity over ice are intercompared with the Microwave Limb Sounder (MLS/Aura) v2.2 data. In general, MIPAS and MLS temperatures agree within ±4 K over the whole pressure range of 316–0.68 hPa. Systematic, latitude-independent differences of −2 to −4 K (MIPAS-MLS) at 121 hPa are explained by previously observed biases in the MLS v2.2 temperature retrievals. Temperature differences of −4 K up to 12 K above 10.0 hPa are present similarly in MIPAS and MLS with respect to ECMWF (European Centre for Medium-Range Weather Forecasts) and are likely due to deficiencies of the ECMWF analysis data. MIPAS and MLS stratospheric volume mixing ratios (vmr) of H2O agree within ±1 ppmv, with indication of oscillations between 146 and 26 hPa in the MLS dataset. Tropical upper tropospheric values of relative humidity over ice measured by the two instruments differ by ±20% in the pressure range ~146 to 68 hPa. These differences are mainly caused by the MLS temperature biases. Ozone mixing ratios agree within 0.5 ppmv (10 to 20%) between 68 and 14 hPa. At pressures smaller than 10 hPa, MIPAS O3 vmr are higher than MLS by an average of 0.5 ppmv (10%). General agreement between MIPAS and MLS HNO3 is within the range of −1.0 (−10%) to 1.0 ppbv (20%). MIPAS HNO3 is 1.0 ppbv (10%) higher compared to MLS in the height range of 46 to 10 hPa over the Northern Hemisphere. Over the tropics at 31.6 hPa MLS shows a low bias of more than 1 ppbv (>50%). In general, MIPAS and MLS N2O vmr agree within 20 to 40 ppbv (20 to 40%). Differences in the height range between 100 to 21 hPa are attributed to a known 20% positive bias in MIPAS N2O data.

scholarly journals Water vapour and ozone profiles in the midlatitude upper troposphere

2005 ◽  
Vol 5 (4) ◽  
pp. 963-971 ◽  
Author(s):  
G. Vaughan ◽  
C. Cambridge ◽  
L. Dean ◽  
A. W. Phillips
Keyword(s):  
Relative Humidity ◽  
Uniform Distribution ◽  
Water Vapour ◽  
Humidity Sensors ◽  
Upper Troposphere ◽  
Peltier Cooling ◽  
Snow White ◽  
Mirror Reflectivity ◽  
Upper Tropospheric Humidity ◽  
Humidity Profiles

Abstract. We present an investigation of upper tropospheric humidity profiles measured with a standard radiosonde, the Vaisala RS80-A, and a commercial frost-point hygrometer, the Snow White. Modifications to the Snow White, to enable the mirror reflectivity and Peltier cooling current to be monitored during flight, were found to be necessary to determine when the instrument was functioning correctly; a further modification to prevent hydrometeors entering the inlet was also implemented. From 23 combined flights of an ozonesonde, radiosonde and Snow White between September 2001 and July 2002, clear agreement was found between the two humidity sensors, with a mean difference of <2% in relative humidity from 2 to 10km, and 2.2% between 10 and 13km. This agreement required a correction to the radiosonde humidity, as described by Miloshevich et al. (2001). Using this result, the dataset of 324 ozonesonde/RS80-A profiles measured from Aberystwyth between 1991 and 2002 was examined to derive statistics for the distribution of water vapour and ozone. Supersaturation with respect to ice was frequently seen at the higher levels - 24% of the time in winter between 8 and 10km. The fairly uniform distribution of relative humidity persisted to 120% in winter, but decreased rapidly above 100% in summer.

scholarly journals MIPAS reduced spectral resolution UTLS-1 mode measurements of temperature, O<sub>3</sub>, HNO<sub>3</sub>, N<sub>2</sub>O, H<sub>2</sub>O and relative humidity over ice: retrievals and comparison to MLS

2009 ◽  
Vol 2 (2) ◽  
pp. 337-353 ◽  
Author(s):  
S. Chauhan ◽  
M. Höpfner ◽  
G. P. Stiller ◽  
T. von Clarmann ◽  
B. Funke ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Pressure Range ◽  
Michelson Interferometer ◽  
Analysis Data ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Latitude Range ◽  
Mixing Ratios ◽  
Medium Range ◽  
The Tropics

Abstract. During several periods since 2005 the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat has performed observations dedicated to the region of the upper troposphere/lower stratosphere (UTLS). For the duration of November/December 2005 global distributions of temperature and several trace gases from MIPAS UTLS-1 mode measurements have been retrieved using the IMK/IAA (Institut für Meteorologie und Klimaforschung/Instituto de Astrofísica de Andalucía) scientific processor. In the UTLS region a vertical resolution of 3 km for temperaure, 3 to 4 km for H2O, 2.5 to 3 km for O3, 3.5 km for HNO3 and 3.5 to 2.5 km for N2O has been achieved. The retrieved temperature, H2O, O3, HNO3, N2O, and relative humidity over ice are intercompared with the Microwave Limb Sounder (MLS/Aura) v2.2 data in the pressure range 316 to 0.68 hPa, 316 to 0.68 hPa, 215 to 0.68 hPa, 215 to 3.16 hPa, 100 to 1 hPa and 316 to 10 hPa, respectively. In general, MIPAS and MLS temperatures are biased within ±4 K over the whole pressure and latitude range. Systematic, latitude-independent differences of −2 to −4 K (MIPAS-MLS) at 121 hPa are explained by previously observed biases in the MLS v2.2 temperature retrievals. Temperature differences of −4 K up to 12 K above 10.0 hPa are present both in MIPAS and MLS with respect to ECMWF (European Centre for Medium-Range Weather Forecasts) and are likely due to deficiencies of the ECMWF analysis data. MIPAS and MLS stratospheric volume mixing ratios (vmr) of H2O are biased within ±1 ppmv, with indication of oscillations between 146 and 26 hPa in the MLS dataset. Tropical upper tropospheric values of relative humidity over ice measured by the two instruments differ by ±20% in the pressure range ~146 to 68 hPa. These differences are mainly caused by the MLS temperature biases. Ozone mixing ratios agree within 0.5 ppmv (10 to 20%) between 68 and 14 hPa. At pressures smaller than 10 hPa, MIPAS O3 vmr are higher than MLS by an average of 0.5 ppmv (10%). General agreement between MIPAS and MLS HNO3 is within the range of −1.0 (−10%) to 1.0 ppbv (20%). MIPAS HNO3 is 1.0 ppbv (10%) higher compared to MLS between 46 hPa and 10 hPa over the Northern Hemisphere. Over the tropics at 31.6 hPa MLS shows a low bias of more than 1 ppbv (>50%). In general, MIPAS and MLS N2O vmr agree within 20 to 40 ppbv (20 to 40%). Differences in the range between 100 to 21 hPa are attributed to a known 20% positive bias in MIPAS N2O data.

scholarly journals Correction Method for RS80-A Humicap Humidity Profiles and Their Validation by Lidar Backscattering Profiles in Tropical Cirrus Clouds

2005 ◽  
Vol 22 (1) ◽  
pp. 18-29 ◽  
Author(s):  
Ulrich Leiterer ◽  
Horst Dier ◽  
Dagmar Nagel ◽  
Tatjana Naebert ◽  
Dietrich Althausen ◽  
...  
Keyword(s):  
Evaluation Method ◽  
Time Lag ◽  
Correction Method ◽  
Cirrus Clouds ◽  
Temperature Dependent ◽  
Upper Troposphere ◽  
Statistical Comparison ◽  
Daily Show ◽  
Tropical Tropopause ◽  
Humidity Profiles

Abstract Routine radiosonde relative humidity (RH) measurements are not reliable as they are presently used in the global upper-air network. The new Lindenberg measuring and evaluation method, which provides RH profile measurements with an accuracy of ±1% RΗ in the temperature range from 35° to −70°C near the tropical tropopause is described. This Standardized Frequencies (FN) method uses a thin-film capacitive polymer sensor of a modified RS90-H Humicap radiosonde. These research humidity reference radiosondes (FN sondes) are used to develop a correction method for operational RS80-A Humicap humidity profiles. All steps of correction and quality control for RS80-A radiosondes are shown: ground-check correction, time-lag and temperature-dependent correction, and the recognition of icing during the ascent. The results of a statistical comparison between FN sondes and RS80-A sondes are presented. Corrected humidity data of operational RS80-A sondes used in Lindenberg (4 times daily) show no bias when compared to FN radiosondes and have an uncertainty of about ±3% RH at the 1 σ or 68% confidence level from 1000 to about 150 hPa. Only a small dry bias of at most −2% RH remains in the lowest part of the boundary layer (up to 500-m height). Finally, some examples of corrected RS80-A RH profiles in cirrus clouds validated by lidar backscattering profiles in a region of the intertropical convergence (Maldive Islands) are demonstrated. The soundings indicate that ice-saturated and ice-supersaturated air above 10-km height were connected with cirrus clouds in all 47 investigated cases, and, second, that the corrected RS80-A RH profiles also provide good quality information on water vapor in the upper troposphere.

scholarly journals Validation of six years of TES tropospheric ozone retrievals with ozonesonde measurements: implications for spatial patterns and temporal stability in the bias

2013 ◽  
Vol 6 (5) ◽  
pp. 1413-1423 ◽  
Author(s):  
W. W. Verstraeten ◽  
K. F. Boersma ◽  
J. Zörner ◽  
M. A. F. Allaart ◽  
K. W. Bowman ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
A Priori ◽  
Temporal Stability ◽  
Lower Troposphere ◽  
Temporal Variations ◽  
Upper Troposphere ◽  
The World ◽  
The Difference ◽  
The Tropics

Abstract. In this analysis, Tropospheric Emission Spectrometer (TES) V004 nadir ozone (O3) profiles are validated with more than 4400 coinciding ozonesonde measurements taken across the world from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) during the period 2005–2010. The TES observation operator was applied to the sonde data to ensure a consistent comparison between TES and ozonesonde data, i.e. without the influence of the a priori O3 profile needed to regulate the retrieval. Generally, TES V004 O3 retrievals are biased high by 2–7 ppbv (7–15%) in the troposphere, consistent with validation results from earlier studies. Because of two degrees of freedom for signal in the troposphere, we can distinguish between upper and lower troposphere mean biases, respectively ranging from −0.4 to +13.3 ppbv for the upper troposphere and +3.9 to +6.0 ppbv for the lower troposphere. Focusing on the 464 hPa retrieval level, broadly representative of the free tropospheric O3, we find differences in the TES biases for the tropics (+3 ppbv, +7%), sub-tropics (+5 ppbv, +11%), and northern (+7 ppbv, +13%) and southern mid-latitudes (+4 ppbv, +10%). The relatively long-term record (6 yr) of TES–ozonesonde comparisons allowed us to quantify temporal variations in TES biases at 464 hPa. We find that there are no discernable biases in each of these latitudinal bands; temporal variations in the bias are typically within the uncertainty of the difference between TES and ozonesondes. Establishing these bias patterns is important in order to make meaningful use of TES O3 data in applications such as model evaluation, trend analysis, or data assimilation.

scholarly journals Carbon and hydrogen isotopic ratios of atmospheric methane in the upper troposphere over the Western Pacific

2012 ◽  
Vol 12 (4) ◽  
pp. 9035-9077 ◽  
Author(s):  
T. Umezawa ◽  
T. Machida ◽  
K. Ishijima ◽  
H. Matsueda ◽  
Y. Sawa ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Isotopic Ratio ◽  
Lower Troposphere ◽  
Western Pacific ◽  
Boreal Summer ◽  
Additional Contribution ◽  
Mixing Ratio ◽  
Upper Troposphere ◽  
The Tropics ◽  
The Western Pacific

Abstract. We present the mixing ratio, δ13C and δD of atmospheric CH4 using commercial aircraft in the upper troposphere (UT) over the Western Pacific for the period December 2005–September 2010. The observed results were compared with those obtained using commercial container ships in the lower troposphere (LT) over the same region. In the Northern Hemisphere (NH), the UT CH4 mixing ratio shows high values in the boreal summer–autumn, when the LT CH4 mixing ratio reaches a seasonal minimum. From tagged tracer experiments made using an atmospheric chemistry transport model, we found that such high CH4 values are due to rapid transport of air masses influenced by CH4 sources in South Asia and East Asia. The observed isotopic ratio data suggest that CH4 sources in these areas have relatively low δ13C and δD signatures, implying biogenic sources. Latitudinal distributions of the annual average UT and LT CH4 mixing ratio intersect each other in the tropics; the mixing ratio value is lower in the UT than in the LT in the NH and the situation is reversed in the Southern Hemisphere (SH), due mainly to the NH air intrusion into the SH through the UT. Such intersection of the latitudinal distributions is observable in δD but not in δ13C, implying additional contribution of a reaction of CH4 with active chlorine in the marine boundary layer. δ13C and δD show low values in the NH and high values in the SH both in the UT and in the LT. We also observed an increase in the CH4 mixing ratio and decreases in δ13C and δD during 2007–2008 in the UT and LT over the Western Pacific, possibly due to enhanced biogenic emissions in the tropics and NH.

Estimating error variances of a microwave sensor and dropsondes aboard the Global Hawk in hurricanes using the three-cornered hat method

2020 ◽  
Author(s):  
Andrew C. Kren ◽  
Richard A. Anthes
Keyword(s):  
Relative Humidity ◽  
Integrated Circuit ◽  
Lower Troposphere ◽  
Specific Humidity ◽  
Data Sets ◽  
Method Error ◽  
Upper Troposphere ◽  
Spatial And Temporal Scales ◽  
Corrected Data ◽  
Global Hawk

AbstractThis study estimates the random error variances and standard deviations (STDs) for four data sets: Global Hawk (GH) dropsondes (DROP), the High-Altitude Monolithic Microwave Integrated Circuit Sounding Radiometer (HAMSR) aboard the GH, the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis, and the Hurricane Weather Research and Forecasting (HWRF) model, using the three-cornered hat (3CH) method. These estimates are made during the 2016 Sensing Hazards with Operational Unmanned Technology (SHOUT) season in the environment of four tropical cyclones from August to October. For temperature and specific and relative humidity, the ERA5, HWRF, and DROP data sets all have similar magnitudes of errors, with ERA5 having the smallest. The error STDs of temperature and specific humidity are less than 0.8 K and 1.0 g kg-1 over most of the troposphere, while relative humidity error STDs increase from less than 5% near the surface to between 10 and 20% in the upper troposphere. The HAMSR bias-corrected data have larger errors, with estimated error STDs of temperature and specific humidity in the lower troposphere between 1.5 and 2.0 K and 1.5 and 2.5 g kg-1. HAMSR’s relative humidity error STD increases from approximately 10% in the lower troposphere to 30% in the upper troposphere. The 3CH method error estimates are generally consistent with prior independent estimates of errors and uncertainties for the HAMSR and dropsonde data sets, although they are somewhat larger, likely due to the inclusion of representativeness errors (differences associated with different spatial and temporal scales represented by the data).

scholarly journals The genesis of Typhoon Nuri as observed during the Tropical Cyclone Structure 2008 (TCS08) field experiment – Part 2: Observations of the convective environment

2011 ◽  
Vol 11 (11) ◽  
pp. 31115-31136 ◽  
Author(s):  
M. T. Montgomery ◽  
R. K. Smith
Keyword(s):  
Tropical Cyclone ◽  
Potential Temperature ◽  
Lower Troposphere ◽  
Vertical Profiles ◽  
Upper Troposphere ◽  
Convective Clouds ◽  
Virtual Potential Temperature ◽  
Noticeable Reduction ◽  
Virtual Temperature ◽  
The Tropics

Abstract. Analyses of thermodynamic data gathered from airborne dropwindsondes during the Tropical Cyclone Structure (2008) experiment are presented for the disturbance that became Typhoon Nuri. Although previous work has suggested that Nuri formed within the protective recirculating "pouch" region of a westward-propagating wave-like disturbance and implicated rotating deep convective clouds in driving the inflow to spin up the tangential circulation of the system-scale flow, the nature of the thermodynamic environment that supported the genesis remains a topic of debate. During the genesis phase, vertical profiles of virtual potential temperature show little variability between soundings on a particular day and the system-average soundings likewise show a negligible change. There is a tendency also for the lower and middle troposphere to moisten. However, the data show that on the scale of the recirculating region of the disturbance, there was no noticeable reduction of virtual temperature in the lower troposphere, but a small warming (less than 1 K) in the upper troposphere. Vertical profiles of pseudo-equivalent potential temperature, θe, during the genesis show a modestly decreasing deficit of θe in the vertical between the surface and a height of minimum θe (between 3 and 4 km), from 17.5 K to 15.2 K. The findings reported here are consistent with that found for developing disturbances observed in the Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT) experiment in 2010. Some implications of the findings are discussed.

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