scholarly journals Influence of tropical cyclones on tropospheric ozone: possible implication

2015 ◽  
Vol 15 (13) ◽  
pp. 19305-19323 ◽  
Author(s):  
S. S. Das ◽  
M. V. Ratnam ◽  
K. N. Uma ◽  
K. V. Subrahmanyam ◽  
I. A. Girach ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Relative Humidity ◽  
Tropical Cyclones ◽  
Tropospheric Ozone ◽  
Potential Temperature ◽  
Lower Troposphere ◽  
Upper Troposphere ◽  
Dry Air ◽  
Cyclonic Storms

Abstract. The present study examines the role of tropical cyclones in the enhancement of tropospheric ozone. The most significant and new observation is the increase in the upper tropospheric (10–16 km) ozone by 20–50 ppbv, which has extended down to the middle (6–10 km) and lower troposphere (< 6 km). The descending rate of enhanced ozone layer is found to be 0.87–1 km day−1. Numerical simulation of potential vorticity, vertical velocity and potential temperature indicate the intrusion of ozone from the upper troposphere to the surface. Space borne observations of relative humidity indicate the presence of sporadic dry air in the upper and middle troposphere over the cyclonic region. These observations constitute quantitatively an experimental evidence of enhanced tropospheric ozone during cyclonic storms.

scholarly journals Influence of tropical cyclones on tropospheric ozone: possible implications

2016 ◽  
Vol 16 (8) ◽  
pp. 4837-4847 ◽  
Author(s):  
Siddarth Shankar Das ◽  
Madineni Venkat Ratnam ◽  
Kizhathur Narasimhan Uma ◽  
Kandula Venkata Subrahmanyam ◽  
Imran Asatar Girach ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Tropospheric Ozone ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Potential Temperature ◽  
Lower Troposphere ◽  
Night Time ◽  
Clear Sky ◽  
Surface Ozone Concentration

Abstract. The present study examines the role of tropical cyclones in the enhancement of tropospheric ozone. The most significant and new observation reported is the increase in the upper-tropospheric (10–16 km) ozone by 20–50 ppbv, which has extended down to the middle (6–10 km) and lower troposphere ( <  6 km). The descent rate of enhanced ozone layer during the passage of tropical cyclone is 0.8–1 km day−1, which is three times that of a clear-sky day (non-convective). Enhancement of surface ozone concentration by  ∼ 10 ppbv in the daytime and 10–15 ppbv in the night-time is observed during a cyclone. Potential vorticity, vertical velocity and potential temperature obtained from numerical simulation, reproduces the key feature of the observations. A simulation study indicates the downward transport of stratospheric air into the troposphere. Space-borne observations of relative humidity indicate the presence of sporadic dry air in the upper and middle troposphere over the cyclonic region. These observations quantitatively constitute experimental evidence of redistribution of stratospheric ozone during cyclonic storms.

The Role of WISHE in the Rapid Intensification of Tropical Cyclones

2020 ◽  
Vol 77 (9) ◽  
pp. 3139-3160
Author(s):  
Chieh-Jen Cheng ◽  
Chun-Chieh Wu
Keyword(s):  
Tropical Cyclones ◽  
Potential Temperature ◽  
Surface Heat ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Rapid Intensification ◽  
Surface Heat Fluxes ◽  
Peak Intensity ◽  
Before And After

Abstract This study examines the role of surface heat fluxes, particularly in relation to the wind-induced surface heat exchange (WISHE) mechanism, in the rapid intensification (RI) of tropical cyclones (TCs). Sensitivity experiments with capped surface fluxes and thus reduced WISHE exhibit delayed RI and weaker peak intensity, while WISHE could affect the evolutions of TCs both before and after the onset of RI. Before RI, more WISHE leads to faster increase of equivalent potential temperature in the lower levels, resulting in more active and stronger convection. In addition, TCs in experiments with more WISHE reach a certain strength earlier, before the onset of RI. During the RI period, more surface heat fluxes could provide convective instability in the lower levels, and cause a consequent development in the convective activity. More efficient intensification in a TC is found with higher surface heat fluxes and larger inertial stability, leading to a stronger peak intensity, more significant and deeper warm core in TC center, and the axisymmetrization of convection in the higher levels. In both stages, different levels of WISHE alter the thermodynamic environment and convective-scale processes. In all, this study supports the crucial role of WISHE in affecting TC intensification rate for TCs with RI.

Life of a Six-Hour Hurricane

2009 ◽  
Vol 137 (1) ◽  
pp. 51-67 ◽  
Author(s):  
Kay L. Shelton ◽  
John Molinari
Keyword(s):  
Deep Convection ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Lower Troposphere ◽  
Vertical Shear ◽  
Vortex Center ◽  
Dry Air ◽  
Sheared Flow ◽  
The Core ◽  
Equivalent Potential

Abstract Hurricane Claudette developed from a weak vortex in 6 h as deep convection shifted from downshear into the vortex center, despite ambient vertical wind shear exceeding 10 m s−1. Six hours later it weakened to a tropical storm, and 12 h after the hurricane stage a circulation center could not be found at 850 hPa by aircraft reconnaissance. At hurricane strength the vortex contained classic structure seen in intensifying hurricanes, with the exception of 7°–12°C dewpoint depressions in the lower troposphere upshear of the center. These extended from the 100-km radius to immediately adjacent to the eyewall, where equivalent potential temperature gradients reached 6 K km−1. The dry air was not present prior to intensification, suggesting that it was associated with vertical shear–induced subsidence upshear of the developing storm. It is argued that weakening of the vortex was driven by cooling associated with the mixing of dry air into the core, and subsequent evaporation and cold downdrafts. Evidence suggests that this mixing might have been enhanced by eyewall instabilities after the period of rapid deepening. The existence of a fragile, small, but genuinely hurricane-strength vortex at the surface for 6 h presents difficult problems for forecasters. Such a “temporary hurricane” in strongly sheared flow might require a different warning protocol than longer-lasting hurricane vortices in weaker shear.

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 Reappraising the appropriate calculation of a common meteorological quantity: Potential Temperature

2020 ◽  
Author(s):  
Manuel Baumgartner ◽  
Ralf Weigel ◽  
Ulrich Achatz ◽  
Allan H. Harvey ◽  
Peter Spichtinger
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Wave Breaking ◽  
Potential Temperature ◽  
Temperature Dependent ◽  
Upper Troposphere ◽  
Dry Air ◽  
Reference Potential ◽  
Definition Of

Abstract. The potential temperature is a widely used quantity in atmospheric science since it is conserved for air's adiabatic changes of state. Its definition involves the specific heat capacity of dry air, which is traditionally assumed as constant. However, the literature provides different values of this allegedly constant parameter, which are reviewed and discussed in this study. Furthermore, we derive the potential temperature for a temperature-dependent parameterization of the specific heat capacity of dry air, thus providing a new reference potential temperature with a more rigorous basis. This new reference shows different values and vertical gradients in the upper troposphere and the stratosphere compared to the potential temperature that assumes constant heat capacity. The application of the new reference potential temperature to the prediction of gravity wave breaking altitudes reveals that the predicted wave breaking height may depend on the definition of the potential temperature used.

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 Remote sensed and in situ constraints on processes affecting tropical tropospheric ozone

2006 ◽  
Vol 6 (6) ◽  
pp. 11465-11520 ◽  
Author(s):  
B. Sauvage ◽  
R. V. Martin ◽  
A. van Donkelaar ◽  
X. Liu ◽  
K. Chance ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Lower Troposphere ◽  
In Situ Measurements ◽  
Top Down ◽  
Upper Troposphere ◽  
In Situ Observations ◽  
Tropospheric O3

Abstract. We use a global chemical transport model (GEOS-Chem) to evaluate the consistency of satellite measurements of lightning flashes and ozone precursors with in situ measurements of tropical tropospheric ozone. The measurements are tropospheric O3, NO2, and HCHO columns from the GOME satellite instrument, lightning flashes from the OTD and LIS instruments, profiles of O3, CO, and relative humidity from the MOZAIC aircraft program, and profiles of O3 from the SHADOZ ozonesonde network. We interpret these multiple data sources with our model to better understand what controls tropical tropospheric ozone. Tropical tropospheric ozone is mainly affected by lightning and convection in the upper troposphere and by surface emissions in the lower troposphere. Scaling the spatial distribution of lightning in the model to the observed flash counts improves the simulation of O3 in the upper troposphere by 5–20 ppbv versus in situ observations and by 1–4 Dobson Units versus GOME retrievals of tropospheric O3 columns. A lightning source strength of 5±2 Tg N/yr best represents in situ observations from aircraft and ozonesonde. Tropospheric NO2 and HCHO columns from GOME are applied to provide top-down constraints on emission inventories of NOx (biomass burning and soils) and VOCs (biomass burning). The top-down biomass burning inventory is larger by a factor of 2 for HCHO and alkenes, and by 2.6 for NOx over northern equatorial Africa. These emissions increase lower tropospheric O3 by 5–20 ppbv, improving the simulation versus aircraft observations, and by 4 Dobson Units versus GOME observations of tropospheric O3 columns. Emission factors in the a posteriori inventory are more consistent with a recent compilation from in situ measurements. The ozone simulation using two different dynamical schemes (GEOS-3 and GEOS-4) is evaluated versus observations; GEOS-4 better represents O3 observations by 5–15 ppbv due to enhanced convective detrainment in the upper troposphere. Heterogeneous uptake of HNO3 on aerosols reduces simulated O3 by 5–7 ppbv, reducing a model bias versus in situ observations over and downwind of deserts. Exclusion of HO2 uptake on aerosols improves O3 by 5 ppbv in biomass burning regions.

scholarly journals Positive and negative influences of typhoons on tropospheric ozone over southern China

2021 ◽  
Vol 21 (22) ◽  
pp. 16911-16923
Author(s):  
Zhixiong Chen ◽  
Jane Liu ◽  
Xugeng Cheng ◽  
Mengmiao Yang ◽  
Hong Wang
Keyword(s):  
Tropospheric Ozone ◽  
Southern China ◽  
Surface Ozone ◽  
Radial Distance ◽  
Lower Troposphere ◽  
Ozone Production ◽  
Ozone Level ◽  
Maximum Enhancement ◽  
Upper Troposphere ◽  
Stratospheric Intrusions

Abstract. Based on an ensemble of 17 typhoons that made landfall between 2014 and 2018, we investigate the positive and negative influences of typhoons on tropospheric ozone over southern China. With respect to the proximity of typhoon centres and the typhoon developmental stages, we find that surface ozone is enhanced when typhoons are 400–1500 km away during the initial stages of development (e.g. from 1 d before to 1 d after typhoon genesis). The positive ozone anomalies reach 10–20 ppbv above the background ozone level on average. The maximum enhancement of surface ozone appears at a radial distance of 1100–1300 km from the typhoon centre during these initial stages. As the typhoons approach southern China, the influences of these systems switch to reducing ozone and, hence, lead to negative ozone anomalies of 6–9 ppbv. Exploring the linkages between ozone variations and typhoon-induced meteorological evolution, we find that increasing temperature and weak winds in the atmospheric boundary layer (ABL) and dominating downward motions promote ozone production and accumulation over the outskirts of typhoons during typhoon initial stages, whereas deteriorating weather, accompanied by dropping temperature, wind gales and convective activity, reduces the production and accumulation of surface ozone when typhoons are making landfall. We further examine the impacts of typhoons on tropospheric ozone profiles vertically, especially the influences of typhoon-induced stratospheric intrusions on lower troposphere and surface ozone. Based on temporally dense ozone profile observations, we find two high-ozone regions, located in the ABL and the middle to upper troposphere respectively, during different typhoon stages. On average, the high-ozone region in the ABL has a maximum ozone enhancement of 10–12 ppbv at 1–1.5 km altitude during the initial typhoon stages. In the high-ozone region in the middle to upper troposphere, ozone enhancement persists over a longer period with a maximum ozone enhancement of ∼ 10 ppbv at 7–8 km altitude shortly after typhoon genesis; this value increases to ∼ 30 ppbv near 12 km altitude when typhoons reach their maximum intensity. When typhoons make landfall, negative ozone anomalies appear and extend upward with a maximum ozone reduction of 14–18 ppbv at 5 km altitude and 20–25 ppbv at 11 km altitude. Although the overall tropospheric ozone is usually reduced during typhoon landfall, we find that five of eight typhoon samples induced ozone-rich air with a stratospheric origin above 4 km altitude; moreover, in three typhoon cases, the ozone-rich air intrusions can sink to the ABL. This suggests that the typhoon-induced stratospheric intrusions play an important role in surface ozone enhancement.

scholarly journals Characterising the Seasonal and Geographical Variability of Tropospheric Ozone, Stratospheric Influence and Recent Changes

2018 ◽  
Author(s):  
Ryan S. Williams ◽  
Michaela I. Hegglin ◽  
Brian J. Kerridge ◽  
Patrick Jöckel ◽  
Barry G. Latter ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
Data Availability ◽  
Ozone Production ◽  
Upper Troposphere ◽  
The World

Abstract. The stratospheric contribution to tropospheric ozone (O3) has been a subject of much debate in recent decades, but is known to have an important influence. Recent improvements in diagnostic and modelling tools provide new evidence that the stratosphere has a much larger influence than previously thought. This study aims to characterise the seasonal and geographical distribution of tropospheric ozone, its variability and changes, and provide quantification of the stratospheric influence on these measures. To this end, we evaluate hindcast specified dynamics chemistry-climate model (CCM) simulations from the ECHAM/MESSy Atmospheric Chemistry (EMAC) model and the Canadian Middle Atmosphere Model (CMAM), as contributed to the IGAC/SPARC Chemistry Climate Model Initiative (CCMI) activity, together with satellite observations from the Ozone Monitoring Instrument (OMI) and ozonesonde profile measurements from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) over a period of concurrent data availability (2005–2010). An overall positive, seasonally dependent bias in 1000–450 hPa (~ 0–5.5 km) subcolumn ozone is found for EMAC, ranging from 2–8 Dobson Units (DU), whereas CMAM is found to be in closer agreement with the observations, although with substantial seasonal and regional variation in the sign and magnitude of the bias (~ −4 to +4 DU). Although the application of OMI averaging kernels (AKs) improves agreement with model estimates from both EMAC and CMAM as expected, comparisons with ozonesondes indicate a positive ozone bias in the lower stratosphere in CMAM, together with an underestimation of photochemical ozone production (negative bias) in the troposphere. Model variability is found to be more similar in magnitude to that implied from ozonesondes, in comparison with OMI which has significantly larger variability. Noting the overall consistency of the CCMs, the influence of the model chemistry schemes and internal dynamics is discussed in relation to the inter-model differences found. In particular, it is shown that CMAM simulates a faster and shallower Brewer-Dobson Circulation (BDC) relative to both EMAC and observational estimates, which has implications for the distribution and magnitude of the downward flux of stratospheric ozone, over the most recent climatological period (1980–2010). Nonetheless, it is shown that the stratospheric influence on tropospheric ozone is larger than previously thought and is estimated to exceed 50 % in the wintertime extratropics, even in the lower troposphere. Finally, long term changes in the CCM ozone tracers are calculated for different seasons between 1980–89 and 2001–10. An overall statistically significant increase in tropospheric ozone is found across much of the world, but particularly in the Northern Hemisphere and in the middle to upper troposphere, where the increase is on the order of 4–6 ppbv (5–10 %). Our model study implies that attribution from stratosphere-troposphere exchange (STE) to such ozone changes ranges from 25–30 % at the surface to as much as 50–80 % in the upper troposphere-lower stratosphere (UTLS) across many regions of the world. These findings highlight the importance of a well-resolved stratosphere in simulations of tropospheric ozone and its implications for the radiative forcing, air quality and oxidation capacity of the troposphere.

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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