Tropospheric Pressure Research Articles

60-Year Cycle in the Earth’s Climate and Dynamics of Correlation Links between Solar Activity and Circulation of the Lower Atmosphere: New Data

In this work we continue studying possible reasons for a roughly 60-year periodicity in the evolution of correlation links between pressure in the lower atmosphere and solar activity. New data providing evidence for influence of the atmospheric circulation regime on the formation of effects of solar activity (galactic cosmic ray fluxes) on tropospheric pressure variations (the development of extratropical baric systems) are presented. It is shown that, in turn, changes in the circulation regime are associated with variations of the intensity of the stratospheric polar vortex, which are also characterized by a ∼60-year periodicity. Dominant harmonics with periods of ∼80 and ∼60 years were revealed in variations of total solar irradiance according to the updated Hoyt–Schatten reconstruction. This allows us to consider variations of solar irradiance as one of possible reasons for changes in the state of the polar vortex and the corresponding changes in large-scale circulation.

Regional, seasonal, and inter-annual variations of Antarctic and sub-Antarctic temperature anomalies related to the Mansurov effect

We use National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data to show that Antarctic surface air temperature anomalies result from differences in the daily-mean duskward component, By, of the interplanetary magnetic field (IMF). We find the statistically-significant anomalies have strong geographical, seasonal, and inter-annual variations. For the interval 1999–2002, regional anomalies poleward of 60°S are of diminishing representative peak amplitude from autumn (3.2 °C) to winter (2.4 °C) to spring (1.6 °C) to summer (0.9 °C). Exploiting apparently simplifying properties in the sub-Antarctic region in autumn 1999–2002, we demonstrate that temperature anomalies in this case are due to geostrophic wind anomalies, resulting from the same By changes, moving air across large meridional gradients in zonal mean air temperature between 50 and 70°S over the 7-hour timescale for which a change in By can be expected to persist. Since the tropospheric pressure anomalies causing these winds have been associated with By-driven anomalies in the electric potential of the ionosphere, we conclude that IMF-induced changes to the global atmospheric electric circuit can cause day-to-day changes in regional surface air temperature of up to several degrees Centigrade.

Manifestation and possible reasons of ∼60-year oscillations in solar-atmospheric links

In this work we continue studying possible reasons for temporal variability observed in correlation links between characteristics of the lower atmosphere and solar activity phenomena at the multidecadal time scale. Temporal variations of correlation coefficients between troposphere pressure at extratropical latitudes and sunspot numbers are compared with the evolution of the large-scale circulation forms according to the Vangengeim-Girs classification, as well as the characteristics of the stratospheric polar vortex and global temperature anomalies. The results obtained show that temporal variability of solar activity/galactic cosmic ray (SA/GCR) effects on troposphere pressure (the development of extratropical baric systems) is characterized by a roughly 60-year periodicity and closely related to changes in the regime of large-scale circulation which accompany transitions between the different states of the polar vortex. It was suggested that the character of SA/GCR effects depends on the polar vortex strength influencing the troposphere-stratosphere coupling. It was shown that the evolution of the polar vortex may be associated with global temperature variations, with a possible reason for these variations being long-term changes of total solar irradiance.

The zonal-mean and regional tropospheric pressure responses to changes in ionospheric potential

Global reanalysis data reveal daily surface pressure responses to changes in the global ionospheric potential in both polar and sub-polar regions. We use 21 years of data to show that the pressure response to externally-induced ionospheric potential changes, that are due to the interplanetary magnetic field east-west (IMF By) component, are present in two separate decadal intervals, and follow the opposite ionospheric potential changes in the Arctic and Antarctic for a given By. We use the 4 years of available data to show that the pressure responses to changes in internally generated ionospheric potential, that are caused by low-latitude thunderstorms and highly electrified clouds, agree in sign and sensitivity with those externally generated. We have determined that the daily varying pressure responses are stronger in local winter and spring. The pressure responses at polar latitudes are predominantly over the Antarctic and Greenland ice caps, and those at sub-polar latitudes are of opposite sign, mainly over oceans. A lead-lag analysis confirms that the responses maximize within two days of the ionospheric potential input. Regions of surface pressure fluctuating by about 4 hPa in winter are found with ionospheric potential changes of about 40 kV. The consistent pressure response to the independent external and internal inputs strongly supports the reality of a cloud microphysical mechanism affected by the global electric circuit. A speculative mechanism involves the ionosphere-earth current density Jz, which produces space charge at cloud boundaries and electrically charged droplets and aerosol particles. Ultrafine aerosol particles, under the action of electro-anti-scavenging, are enabled to grow to condensation nuclei size, affecting cloud microphysics and cloud opacity and surface pressure on time scales of hours.

Atmospheric, radiative, and hydrologic effects of future land use and land cover changes: A global and multimodel climate picture

AbstractLand use and land cover changes (LULCC) modulate land surface energy, heat, moisture, and momentum fluxes. Using simulations performed with and without LULCC for five earth system models, averaged over the 2071–2100 period, we quantify the biophysical effects in response to a future realistic LULCC scenario (Representative Concentration Pathway RCP8.5) on 15 climate variables (i.e., atmospheric, radiative, wind, hydrologic variables, and heat fluxes). We find that climate models are able to simulate some robust and strong climate perturbations in response to LULCC. In tropical regions with substantial LULCC, significantly higher skin temperatures, less precipitation and soil moisture, less evaporation and clouds, more incoming radiation and stronger winds, more anticyclonic conditions and subsidence, are simulated in response to future LULCC. In midlatitude and high latitude, LULCC result in autumn cooling and higher tropospheric pressures, while East Asia is drier, warmer, with higher sensible heat flux and lower evaporation. The tropical wind strengthening and weakening of the hydrological cycle are comparable in magnitude to their future regional changes induced by greenhouse gases under RCP8.5, which make LULCC an indispensable forcing to take into account in future climatic assessments. Finally, our study reveals significant indirect atmospheric processes triggered by LULCC, implying substantial changes in incoming radiation, which dominate climatic responses over the direct effects, particularly in boreal regions.

Theoretical Model of the Tropospheric Pressure Variation on the Height

Theoretical Model of the Tropospheric Pressure Variation on the Height

An investigation on the origin of regional springtime ozone episodes in the western Mediterranean

Abstract. For the identification of regional springtime ozone episodes, rural European Monitoring and Evaluation Programme (EMEP) ozone measurements from countries surrounding the western Mediterranean (Spain, France, Switzerland, Italy, Malta) have been examined with emphasis on periods of high ozone-mixing ratios, according to the variation of the daily afternoon (12:00–18:00) ozone values. For two selected high ozone episodes in April and May 2008, composite NCEP/NCAR reanalysis maps of various meteorological parameters and/or their anomalies (geopotential height, specific humidity, vertical wind velocity omega, vector wind speed and temperature) at various tropospheric pressure levels have been examined together with the corresponding satellite Infrared Atmospheric Sounding Interferometer (IASI) ozone measurements (at 3 and 10 km), CHIMERE simulations, vertical ozone soundings and HYSPLIT back trajectories. The observations show that high ozone values are detected in several countries simultaneously over several days. Also, the examined spring ozone episodes over the western Mediterranean and in central Europe are linked to synoptic meteorological conditions very similar to those recently observed in summertime ozone episodes over the eastern Mediterranean (Kalabokas et al., 2013, 2015; Doche et al., 2014), where the transport of tropospheric ozone-rich air masses through atmospheric subsidence significantly influences the boundary layer and surface ozone-mixing ratios. In particular, the geographic areas with observed tropospheric subsidence seem to be the transition regions between high-pressure and low-pressure systems. During the surface ozone episodes IASI satellite measurements show extended areas of high ozone in the lower- and upper-troposphere over the low-pressure system areas, adjacent to the anticyclones, which influence significantly the boundary layer and surface ozone-mixing ratios within the anticyclones by subsidence and advection in addition to the photochemically produced ozone there, resulting in exceedances of the 60 ppb standard.

Atmospheric pressure variations at extratropical latitudes associated with Forbush decreases of galactic cosmic rays

Changes of troposphere pressure associated with short-time variations of galactic cosmic rays (GCRs) taking place in the Northern hemisphere’s cold months (October–March) were analyzed for the period 1980–2006, NCEP/NCAR reanalysis data being used. Noticeable pressure variations during Forbush decreases of GCRs were revealed at extratropical latitudes of both hemispheres. The maxima of pressure increase were observed on the 3rd–4th days after the event onsets over Northern Europe and the European part of Russia in the Northern hemisphere, as well as on the 4th–5th days over the eastern part of the South Atlantic opposite Queen Maud Land and over the d’Urville Sea in the Southern Ocean. According to the weather chart analysis, the observed pressure growth, as a rule, results from the weakening of cyclones and intensification of anticyclone development in these areas. The presented results suggest that cosmic ray variations may influence the evolution of extratropical baric systems and play an important role in solar-terrestrial relationships.

Stratospheric polar vortex as a possible reason for temporal variations of solar activity and galactic cosmic ray effects on the lower atmosphere circulation

Possible reasons for the temporal instability of long-term effects of solar activity (SA) and galactic cosmic ray (GCR) variations on the lower atmosphere circulation were studied. It was shown that the detected earlier ∼60-year oscillations of the amplitude and sign of SA/GCR effects on the troposphere pressure at high and middle latitudes (Veretenenko and Ogurtsov, Adv.Space Res., 2012) are closely related to the state of a cyclonic vortex forming in the polar stratosphere. The intensity of the vortex was found to reveal a roughly 60-year periodicity affecting the evolution of the large-scale atmospheric circulation and the character of SA/GCR effects. An intensification of both Arctic anticyclones and mid-latitudinal cyclones associated with an increase of GCR fluxes at minima of the 11-year solar cycles is observed in the epochs of a strong polar vortex. In the epochs of a weak polar vortex SA/GCR effects on the development of baric systems at middle and high latitudes were found to change the sign. The results obtained provide evidence that the mechanism of solar activity and cosmic ray influences on the lower atmosphere circulation involves changes in the evolution of the stratospheric polar vortex.

Long-term trends and decadal solar variability in ozone near the tropopause over the Indian region

To investigate the long-term trends and effects of decadal solar variability in the upper tropospheric ozone, data obtained from the Stratospheric Aerosol and Gas Experiment II (SAGE II) aboard the Earth Radiation Budget Satellite (ERBS) during the period 1985–2005 were analysed using a multifunctional regression model over the Indian region (8–40° N; 65–100° E). Analysis of time series spanning these years shows statistically insignificant trends (at the two-sigma level (95% confidence level)) at upper tropospheric pressure levels (10−16 km). This period covers two solar cycles, one lasting from 1985 to 1995 and the other from 1996 to 2005; these are referred to as decade I and decade II, respectively. Since temporal variation in ozone number density indicates 11 year periodicity, trends are statistically significant when calculated separately during each solar cycle. Trend analysis indicates statistically significant positive trends (0.7 ± 1.7% to 3.9 ± 2.9% year−1 during decade I, and 2.2 ± 1.6% to 4.5 ± 3.0% year−1 during decade II). In general, higher ozone trends are observed during decade II. Seasonal variation in trends during decade II shows increasing trends during the pre-monsoon (0.8−3.8% year−1), monsoon (0.8−7.1% year−1), and post-monsoon (2.8−8.0% year−1) seasons. The annually averaged solar signal in ozone is found to be of the order of around −5 ± 4.3% to −13.8 ± 6.7%/(100 sfu). Results obtained in the present study are also compared with those obtained by other researchers.

Atmospheric impacts of an Arctic sea ice minimum as seen in the Community Atmosphere Model

AbstractThere is growing recognition that reductions in Arctic sea ice extent will influence patterns of atmospheric circulation both within and beyond the Arctic. We explore the impact of 2007 ice conditions (the second lowest Arctic sea ice extent in the satellite era) on atmospheric circulation and surface temperatures and fluxes through a series of model experiments with the NCAR Community Atmospheric Model version 3 (CAM3). Two 30‐year simulations were performed; one using climatological sea ice extent for the end of the 20th century and other using observed sea ice extent from 2007. Circulation differences over the Northern Hemisphere were most prominent during autumn and winter with lower sea level pressure (SLP) and tropospheric pressure simulated over much of the Arctic for the 2007 sea ice experiment. The atmospheric response to 2007 ice conditions was much weaker during summer, with negative SLP anomalies simulated from Alaska across the Arctic to Greenland. Higher temperatures and larger surface fluxes to the atmosphere in areas of anomalous open water were also simulated. CAM3 experiment results were compared to observed SLP anomalies from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis data. The observed SLP anomalies during spring are nearly opposite to those simulated. In summer, large differences were shown between the observed and simulated SLP also, suggesting that the sea ice conditions in the months preceding and during the summer of 2007 were not responsible for creating an atmospheric circulation pattern which favoured the large observed sea ice loss. The simulated and observed atmospheric circulation anomalies during autumn and winter were more similar than spring and summer, with the exception of a strong high pressure system in the Beaufort Sea which was not simulated, suggesting that the forced atmospheric response to reduced sea ice was in part responsible for the observed atmospheric circulation anomalies during autumn and winter.

The stratospheric polar vortex as a cause for the temporal variability of solar activity and galactic cosmic ray effects on the lower atmosphere circulation

In this work we continue studying possible reasons for the temporal variability of long-term effects of solar activity (SA) and galactic cosmic ray (GCR) variations on the lower atmosphere circulation. It was shown that long-term oscillations of the amplitude and sign of SA/GCR effects on troposphere pressure at high and middle latitudes are closely related to the state of a cyclonic vortex forming in the polar stratosphere. A roughly 60-yr periodicity was revealed in the vortex strength affecting the evolution of the large-scale atmospheric circulation and the sign of SA/GCR effects. The results obtained suggest an important part of the polar vortex in the mechanism of SA/GCR influence on the troposphere circulation.

Validation of an extractive, airborne, compact TDL spectrometer for atmospheric humidity sensing by blind intercomparison

Accuracy, precision, repeatability and long-term stability, are the most important requirements to enable reliable airborne humidity measurements, which are needed for climate models or to validate e.g. remote sensing instrumentation like satellites. However, various hygrometer artifacts which depend on the individual sensor principle and the application profile frequently cause problems and significantly complicate the hygrometer choice. Sensor intercomparisons are one way of providing the information for an optimal choice.In this paper we present the first part of a blind, static, laboratory-based intercomparison of a new, calibration-free, 1.4 μm diode laser-based, optical hygrometer (SEALDH) with the two most important measurement principles for airborne hygrometry (frost-point hygrometers, FPH, and Lyman-alpha fluorescence hygrometers, LAFH). During three days of measurement, the TDL-hygrometer achieved a H2O resolution of up to 0.5 ppmv (Δt=2 sec) at tropospheric pressure and H2O concentration levels (100–800 hPa, 10 to 8000 ppmv H2O). Its absolute accuracy was investigated via blind intercomparison with two reference FPHs and a LAFH. Without any calibration of SEALDH, i.e. without a comparison to a water vapor standard, we achieve an excellent agreement with the reference sensors, with an average systematic offset (over all three days) of −3.9 %±1.5 %, which is fully consistent with the sensor’s uncertainty bounds.Further we also reevaluated the SEALDH data of day 2 and 3 in a calibrated mode using an independent set of FPH data from the first day and found an 8-fold accuracy improvement, yielding an excellent overall relative deviation of only 0.52 %±1.5 % with respect to a LAFH and a D/FH sensor.

The Reliability of Antarctic Tropospheric Pressure and Temperature in the Latest Global Reanalyses

Abstract In this study, surface and radiosonde data from staffed Antarctic observation stations are compared to output from five reanalyses [Climate Forecast System Reanalysis (CFSR), 40-yr ECMWF Re-Analysis (ERA-40), ECMWF Interim Re-Analysis (ERA-Interim), Japanese 25-year Reanalysis (JRA-25), and Modern Era Retrospective-Analysis for Research and Applications (MERRA)] over three decades spanning 1979–2008. Bias and year-to-year correlation between the reanalyses and observations are assessed for four variables: mean sea level pressure (MSLP), near-surface air temperature (Ts), 500-hPa geopotential height (H500), and 500-hPa temperature (T500). It was found that CFSR and MERRA are of a sufficiently high resolution for the height of the orography to be accurately reproduced at coastal observation stations. Progressively larger negative Ts biases at these coastal stations are apparent for reanalyses in order of decreasing resolution. However, orography height bias cannot explain large winter warm biases in CFSR, JRA-25, and MERRA (11.1°, 10.2°, and 7.9°C, respectively) at Amundsen–Scott and Vostok, which have been linked to problems with representing the surface energy balance. Linear trends in the annual-mean T500 and H500 averaged over Antarctica as a whole were found to be most reliable in CFSR, ERA-Interim, and MERRA, none of which show significant trends over the period 1979–2008. In contrast JRA-25 shows significant negative trends over 1979–2008 and ERA-40 gives significant positive trends during the 1980s (evident in both T500 and H500). Comparison to observations indicates that the positive trend in ERA-40 is spurious. At the smaller spatial scale of individual stations all five reanalyses have some spurious trends. However, ERA-Interim was found to be the most reliable for MSLP and H500 trends at station locations.

The dynamics of solar activity and anomalous weather of summer 2010: 2. Relationship with the active longitude zone; effects in the west and east

We confirm the close synoptic relationship of the sectoral structure of the Sun’s magnetic field of the with the near-Earth tropospheric pressure with a case study of three European points (Troitsk, Rome, Jungfrau) in the period of the anomalously hot summer of June–August 2010. We substantiate the position that such a relationship was fostered by the anomalously low solar activity as a result of superposition of the minima of the 22- and 180-year cycles. Sectoral analysis of the solar-tropospheric relationships has shown that the appearance of a blocking anticyclone in the Moscow suburbs, its expansion to Rome and Jungfrau, and subsequent retreat at first from these points, and then from the Moscow suburbs was closely related to solar activity phenomena producing, according to contemporary notions, cyclonic activity, shown by simulation of the Earth’s electric field.

Relationship between Reduction of Summer Precipitation in North China and Atmospheric Circulation Anomalies

Based on Reanalysis datasets from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and summer rainfall datasets from China National Climate Center (NCC), by using trend analysis and composite analysis methods, the relationship between the reduction of summer precipitation in North China and northern hemispheric circulation changes was investigated. The results show that summer rainfall in North China had a significant decreasing tendency, especially true since 1965 in which an abrupt change occurred. The northern hemisphere atmospheric circulation at 500 hPa had a remarkable change after 1965, from outstanding meridional circulation to outstanding zonal circulation, leading to upper trough activity to decrease, resulting in the rainfall weather processes caused by upward motion behind trough significantly to reduce. At 500 hPa in Mongolian region, air temperature decreased, resulting in lower troposphere pressure to increase, leading to low pressure activity significantly to decrease and rainfall weather processes influencing North China to reduce. At the same time, the decreased air temperature in 500 hPa would caused the upper troposphere geopotential height to reduce, resulting in high–altitude jet southerly location, the East Asian summer monsoon to weaken, then it was difficult for water vapor transport to cross the Yangtze River valley and reach the North China region, with a southerly summer monsoon rainfall zone. The summer precipitation reduction in North China had a good correlation with the northern hemispheric circulation changes.

NOx production in laboratory discharges simulating blue jets and red sprites

Sources of middle atmosphere nitrogen oxides, including transport from the troposphere and production in situ by energetic electrons, are currently not well characterized. Production of nitrogen oxides (NOx) in the middle atmosphere by transient luminous events (TLEs), such as red sprites and blue jets has previously been estimated from satellite observations and modeling studies. This is the first laboratory attempt to estimate NOx production by TLEs, following studies that have confirmed electrical similarities between laboratory discharges and TLEs. A pressure‐controlled chamber and high‐voltage power supplies simulated middle atmosphere discharges. Chemiluminescence NOx analyzers sampled NOx following the completion of the chamber discharges, which was used to calculate total NOx production for each discharge as well as NOx per ampere of current and NOx per Joule of discharge energy. Three different production efficiencies in NOx/J as a function of pressure pointed to three different production regimes: one for tropospheric pressures (100–500 mb), one for stratospheric pressures (1–100 mb), and one for upper stratospheric to mesospheric pressures (no greater than 1 mb). Discharges at jet‐like pressures are measured to produce 1.7 × 1016 to 6.40 × 1017 molecules of NOx per discharge, while discharges at sprite‐like pressure produce 6.97 × 1013 to 8.57 × 1013 molecules of NOx per discharge. Blue jets were calculated to produce 1.7 × 1022 to 7.4 × 1026 molecules of NOx, while red sprites were calculated to produce 6.8 × 1023 to 6.3 × 1027 molecules of NOx. On the basis of global sprite frequency estimates global annual NOx production by sprites is estimated to be between 7 × 1023 and 2 × 1028 molecules per second.

Decadal northward shift of the Meiyu belt and the possible cause

The feature of the decadal movement of the Meiyu belt and their association with East Asia atmospheric circulation for the period of 1979–2007 is examined in this study. It is shown that the Meiyu belt of China has a decadal shift in the late 1990s. There is a remarkable difference between the periods before and after 1999, with the Meiyu belt mainly located to the south of the Yangtze River valley before 1999, but afterward mainly located in the Huaihe River valley. At the same time, a distinctive tropospheric warming and stratospheric cooling trend is found in the mid-latitudes of East Asia, which causes the upper tropospheric pressure surfaces upward bulging and the tropoause elevated in the subtropics and associated widening of the subtropical area over East Asia. Accompanying the subtropics widening, the subtropical westerly jet over East Asia shifts northward and the East Asia tropical Hadley circulation expands poleward, which results in the northward shift of the Meiyu belt.

Reaction of gaseous mercury with molecular iodine, atomic iodine, and iodine oxide radicals — Kinetics, product studies, and atmospheric implications

Mercury is present in the Earth’s atmosphere mainly in elemental form. The chemical transformation of mercury in the atmosphere may influence its bioaccumulation in the human food chain as well as its global cycling. We carried out the first kinetic and product studies of the reactions of gaseous mercury with molecular iodine, atomic iodine, and iodine oxide radicals at tropospheric pressure (~740 Torr) and 296 ± 2 K in air and in N2 (1 Torr = 133.322 4 Pa; 0 °C = 273.15 K). Atomic iodine was formed using UV photolysis of CH2I2. IO radicals were formed by the UV photolysis of CH2I2 in the presence of ozone The reaction kinetics were studied using absolute rate techniques with gas chromatographic and mass spectroscopic detection (GC–MS). The measured rate coefficient for the reaction of Hg0 with I2 was ≤ (1.27 ± 0.58) × 10–19 cm3 molecule–1 s–1. The reaction products were analyzed in the gas phase from the suspended aerosols and from deposits on the walls of the reaction chambers using six complementary methods involving chemical ionization and electron impact mass spectrometry, GC–MS, a MALDI-TOF mass spectrometer, a cold vapor atomic fluorescence spectrometer (CVAFS), and a high-resolution transmission electron microscope (HRTEM) coupled to an energy dispersive spectrometer (EDS). The major reaction products identified were HgI2, HgO, and HgIO or HgOI. The implications of the results are discussed with regards to both the chemistry of atmospheric mercury and its potential implications in the biogeochemical cycling of mercury.Key words: mercury, molecular iodine, atomic iodine, iodine oxide radicals kinetics, product study, atmospheric chemistry.

Validation of Aura Microwave Limb Sounder water vapor by balloon‐borne Cryogenic Frost point Hygrometer measurements

Here we present extensive observations of stratospheric and upper tropospheric water vapor using the balloon‐borne Cryogenic Frost point Hygrometer (CFH) in support of the Aura Microwave Limb Sounder (MLS) satellite instrument. Coincident measurements were used for the validation of MLS version 1.5 and for a limited validation of MLS version 2.2 water vapor. The sensitivity of MLS is on average 30% lower than that of CFH, which is fully compensated by a constant offset at stratospheric levels but only partially compensated at tropospheric levels, leading to an upper tropospheric dry bias. The sensitivity of MLS observations may be adjusted using the correlation parameters provided here. For version 1.5 stratospheric observations at pressures of 68 hPa and smaller MLS retrievals and CFH in situ observations agree on average to within 2.3% ± 11.8%. At 100 hPa the agreement is to within 6.4% ± 22% and at upper tropospheric pressures to within 23% ± 37%. In the tropical stratosphere during the boreal winter the agreement is not as good. The “tape recorder” amplitude in MLS observations depends on the vertical profile of water vapor mixing ratio and shows a significant interannual variation. The agreement between stratospheric observations by MLS version 2.2 and CFH is comparable to the agreement using MLS version 1.5. The variability in the difference between observations by MLS version 2.2 and CFH at tropospheric levels is significantly reduced, but a tropospheric dry bias and a reduced sensitivity remain in this version. In the validation data set a dry bias at 177.8 hPa of −24.1% ± 16.0% is statistically significant.