Atmospheric Research Research Articles

Global tropopause height determination using GNSS radio occultation

The tropopause layer is a crucial stratum of the earth's atmosphere that attracts more interest from climate and atmospheric researchers. The observables of the global navigation satellite system (GNSS) allow for continuous and long-term research of the atmosphere. The Meteorological Operational Satellite Program (MetOp) mission has a large number of radio occultation (RO) events globally with a high vertical resolution. For investigating the atmosphere, GNSS RO is regarded as a great active remote sensing approach. The present paper investigates the tropopause height (TPH) globally using 5,738,483 GNSS RO measurements of MetOp from 2007 to 2021 to analyze the monthly and yearly variability patterns of TPHs. The spatiotemporal variation of TPH confirms a bell shape. According to the analysis, the TPH varies with latitude, with the highest level reaching up to 17 km in the equatorial region and decreasing gradually to get its lowest value of 8 km at the poles. The global TPH estimated from GNSS RO is very well matched with the TPH estimated from the ECMWF Reanalysis v5 (ERA5) model with a correlation of 0.9997 in 2021. The findings of this study will contribute to a better understanding of TPH variations. As a result, our findings may be helpful in advancing atmospheric modeling and estimating wet delay for GNSS observations.

Observation of the vertical structure of atmospheric boundary layer in subtropical UHI by radiosonde

Existing studies on the urban heat island (UHI) effect tend to focus on the planar scale. However, the UHI effect has obvious three-dimensional properties. This research focuses on the vertical structure of UHI. The study combined big data from sounding balloon and surface measurements in the Database for Atmospheric and Hydrologic Research, Taiwan. Data organization and classification were conducted using the Python programming language, the NumPy mathematical function library, and the Pandas data manipulation library. Results confirmed the existence of the atmospheric boundary layer and the canopy. Furthermore, the temperature inversion of the atmospheric boundary layer fell between heights of 130 m and 667 m. The height of the inversion is affected by the wind speed and cloudiness. Thereby demonstrating that the inversion fluctuates with weather scenario changes. The research results can be applied as the direction of urban planning thinking for urban heat island countermeasures.

Comparative Accuracies of Models for Drag Prediction During Geomagnetically Disturbed Periods: A First Principles Model Versus Empirical Models

AbstractWe examine the accuracy of density prediction by the first principles model Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) developed by the National Center for Atmospheric Research and compare it to the accuracy of three empirical models: Jacchia 71, the Naval Research Laboratory Mass Spectrometer Incoherent Scatter Extended 2000 (NRLMSIS), Jacchia 1971, and Jacchia‐Bowman 2008. Comparisons are made for three large storms: the October 2003 storm, the March 2013 storm, and the March 2015 storm. To evaluate the accuracy of these models we use tracking data for nine space objects in low Earth orbit. Additionally, we evaluate the accuracy of the TIEGCM and NRLMSIS with data from high precision accelerometers on the Challenging Minisatellite Payload (CHAMP) and Gravity field and Circulation Explorer (GOCE) satellites. The goal is to assess the use of a first principles model as a potential tool for forecasting satellite drag during large magnetic storms. For the storms considered, we found the TIEGCM, JB2008, and NRLMSIS models to be substantially more accurate than the Jacchia 71 model. The accuracies of the TIEGCM and JB2008 models were similar, but overall, the TIEGCM was more accurate. We found smaller differences for TIEGCM versus CHAMP than for NRLMIS for the Halloween Storm, and smaller differences than results published for JB2008 and the assimilative model HASDM. The empirical models are at present more practical for operational purposes, but the TIEGCM, developed as a research model, with a greater focus on operational use offers the potential for improved utility during stressing conditions.

Evaluation of Spatial Gas Temperature and Water Vapor Inhomogeneities in TDLAS in Circular Multipass Absorption Cells Used for the Analysis of Dynamic Tube Flows.

The use of optical circular multipass absorption cells (CMPAC) in an open-path configuration enables the sampling free analysis of cylindrical gas flows with high temporal resolution and only minimal disturbances to the sample gas in the pipe. Combined with their robust unibody design, CMPACs are a good option for many applications in atmospheric research and industrial process monitoring. When deployed in an open-path configuration, the effects of inhomogeneities in the gas temperature and composition have to be evaluated to ensure that the resulting measurement error is acceptable for a given application. Such an evaluation needs to consider the deviations caused by spectroscopic effects, e.g., nonlinear effects of temperature variations on the intensity of the spectral line, as well as the interaction of the temperature and concentration field with the characteristic laser beam pattern of the CMPAC. In this work we demonstrate this novel combined evaluation approach for the CMPAC used as part of the tunable diode laser absorption spectroscopy (TDLAS) reference hygrometer in PTB's dynH2O setup for the characterization of the dynamic response behavior of hygrometers. For this, we measured spatially resolved, 2D temperature and H2O concentration distributions, and combined them with spatially resolved simulated spectra to evaluate the inhomogeneity effects on the line area of the used H2O spectral line at 7299.43 cm-1. Our results indicate that for dynH2O, the deviations caused by the interaction between large concentration heterogeneities and the characteristic sampling of the beam pattern of the CMPAC are three orders of magnitude larger than deviations caused by small temperature heterogeneity induced spectroscopic effects. We also deduce that the assumption that the "path-integrated" H2O concentration derived with the open-path CMPAC setup represents an accurate H2O area average in the flow section covered by the CMPAC in fact shows significant differences of up to 16% and hence does not hold true when large H2O concentration gradients are present.

Demonstration of a Nowcasting Service for High Ice Water Content (HIWC) Conditions

Areas of high ice water content (HIWC) within cloud systems may cause power loss events and engine damage in jet aircraft due to ice crystal icing (ICI). The Algorithm for Prediction of HIWC Areas (ALPHA) was developed to identify these regions and enable provision of guidance to airlines. ALPHA combines numerical weather prediction model data, satellite data, and radar data (where available), and applies fuzzy logic to identify the likely presence of HIWC. In a collaboration between the U.S. National Center for Atmospheric Research, Australian Bureau of Meteorology, U.S. Federal Aviation Administration, and Australian airlines, a trial of ALPHA was conducted for an area across Indonesia, Papua New Guinea (PNG), and northern Australia, a region with frequent deep convection and a relatively high incidence of ICI events. ALPHA was adapted to ingest data from the Australian Community Climate and Earth System Simulator model and the Japanese Himawari-8 geostationary meteorological satellite. Radar data was not used. The HIWC product was made available to stakeholder groups for evaluation. Independent validation of the HIWC product was undertaken by comparing it with retrieved profiles of ice water content (IWC) from the cloud profiling radar on the NASA polar-orbiting CloudSat satellite. Conduct of the ALPHA trial and results from validation of the HIWC product provides confidence in the potential utility for flight planning, maintaining situational awareness, and flight monitoring.

Further Discussion on Temperature Field During Storms and Thermal Score in Typhoon Actives and Damages of Typhoons

Background: As we know, tropical cyclones or hurricanes (TCs) and typhoons are one of the natural disasters causing considerable damage to our life, economy and society. Objective: This study goal is to explore damages of typhoons and the temperature field during storms operating in the East Sea under the influence of cold air over time. Methodology: To determine the activities of the cold surge, the study analyzes the evolution of the 24-hour sea level barometric value in the region of 20-250N; 105-1150E. This is the area that is often affected first when KKL operates in East Asia in general and Vietnam in particular. Then, cold surge is considered to affect the area when the 24-hour transformer has a value greater than 1hPa. Results: Studies showed that the effects were investigated from 1991 to 2011 based on archived data from the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP-NCAR) and the number of typhoons were sourced from the International Best Track Archive for Climate Stewardship (IBTrACS). Conclusion: research showed that most typhoons occurred in August and September, which was related to high temperature in the summer season and the southwest monsoon in the area. In Vietnam, Although Typhoons has dissipated, the rain after typhoon No. 4 has left 3 people dead and missing, more than 7,000 houses were flooded, tens of thousands of hectares of agriculture and fisheries were damaged.

Improving the Hufnagel-Andrews-Phillips refractive index structure parameter model using turbulent intensity.

This paper proposes a modification of the Hufnagel-Andrews-Phillips (HAP) Refractive Index Structure Parameter model that will better characterize the HAP profile against experimental data using the turbulent intensity, which is the ratio of wind speed variance to the average wind speed-squared, and Korean Refractive Index Parameter yearly statistics, Comparisons between this modified HAP model, the Critical Laser Enhancing Atmospheric Research 1 (CLEAR 1) profile model and several of the data sets are made. These comparisons highlight that this new model offers a more consistent representation of the averaged experimental data profiles than the CLEAR 1 model did. In addition, comparisons between this model and various experimental data set reported in the literature will show good agreement between the model and averaged data, and reasonable agreement with non-averaged data sets. This improved model should prove useful in system link budget estimates and atmospheric research.

An in situ cosmogenic 14C extraction system at the Atmosphere and Ocean Research Institute, The University of Tokyo

In situ14C surface exposure dating is a powerful tool for understanding the Earth’s surface processes during the late Quaternary. This study developed an in situ14C extraction system that heats samples to 1650 °C to extract in situ14C from quartz. The initial experiments showed a high blank level (1.80 × 107 14C atoms) and low extraction efficiency (5.36%). Each procedural step required a blank test to understand the cause of the high background, and the results identified several components of the extraction system as sources of 14C contamination. After improving the apparatus design, the new system showed a sufficiently low blank level (5.32 × 104 14C atoms). The extraction efficiency ranged from 111% to 127% with this system. These results show that the system is capable of extracting in situ14C from quartz for surface exposure dating.

Case Study of a Mesospheric Temperature Inversion over Maïdo Observatory through a Multi-Instrumental Observation

The dynamic vertical coupling in the middle and lower thermosphere (MLT) is documented over the Maïdo observatory at La Réunion island (21°S, 55°E). The investigation uses data obtained in the framework of the Atmospheric dynamics Research InfraStructure in Europe (ARISE) project. In particular, Rayleigh lidar and nightglow measurements combined with other observations and modeling provide information on a mesospheric inversion layer (MIL) and the related gravity waves (GWs) on 9 and 10 October 2017. A Rossby wave breaking (RWB) produced instabilities in the sheared background wind and a strong tropospheric activity of GWs on 9–11 October above La Réunion. The MIL was observed on the night of 9 October when a large amount of tropospheric GWs propagated upward into the middle atmosphere and disappeared on 11 October when the stratospheric zonal wind filtering became a significant blocking. Among other results, dominant mesospheric GW modes with vertical wavelengths of about 4–6 km and 10–13 km can be traced down to the troposphere and up to the mesopause. Dominant GWs with a wavelength of ~2–3 km and 6 km also propagated upward and eastward from the tropospheric source into the stratosphere on 9–11 October. Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature and OH profiles indicate that GW activity in the middle atmosphere affects the upper atmosphere with waves breaking at heights below the MIL and in the mesopause. Several techniques are illustrated on nightglow images to access GW activity and spectral characteristics at the mesopause for high and low frequency GWs on the nights of 9–10 October. In conclusion, intense tropospheric activity of GWs induced by RWB events can be linked with MILs at the subtropical barrier in the South-West Indian Ocean during austral winter.

Reflections on the Scientific Legacy of Sergej S. Zilitinkevich on PBL and Urban Parameterizations in NWP Models

The paper summarizes many of the scientific achievements of Professor Sergej S. Zilitinkevich (1936–2021). It first focuses on his basic and applied atmospheric boundary layer research contributions. It then reviews their applications within research and operational numerical weather prediction and air quality modeling, showing their contribution to solving modeling problems related to extremely-stable and -unstable boundary layers.

Climate Network Analysis Detects Hot Spots under Anthropogenic Climate Change

Anthropogenic climate change poses a significant threat to both natural and social systems worldwide. In this study, we aim to identify regions most impacted by climate change using the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP-NCAR) reanalysis of near-surface daily air temperature data spanning 73 years (1948–2020). We develop a novel climate network framework to identify “hot spots”, regions that exhibit significant impact or impacted characteristics. Specifically, we use the node degree, a fundamental feature of the network, to measure the influence of each region and analyze its trend over time using the Mann–Kendall test. Our findings reveal that the majority of land areas experiencing increasing degrees are more closely connected to other regions, while the ocean shows the opposite trend due to weakened oceanic circulations. In particular, the degree in the central Pacific Ocean’s El Niño region is significantly reduced. Notably, we identify three “hot spots” in East Asia, South America, and North Africa, respectively, with intensive increasing network degree fields. Additionally, we find that the hot spot in East Asia is teleconnected to remote regions, such as the South Pacific, Siberia, and North America, with stronger teleconnections in recent years. This provides a new perspective for assessing the planetary impacts of anthropogenic global warming. By using a novel climate network framework, our study highlights regions that are most vulnerable to the effects of climate change and emphasizes the importance of understanding network structures to assess the global impacts of anthropogenic climate change.

Current AMO mitigating extreme high temperatures in Central Asia under global warming

AbstractUnder global warming, extreme high temperatures (EHTs) have become frequent and enhanced around the world. However, we found that the frequency and intensity of EHTs in Central Asia (CA) are decreasing over the last four decades when the effects of climate warming are removed. From 1979 to 2020, an interdecadal shift in CA's EHTs occurred around the mid‐1990s, preceded by high values (1983–1997) and followed by low values (1998–2016). The observational analysis and numerical simulations using National Center for Atmospheric Research Community Atmosphere Model version 5.3 both demonstrate that the phase transition of Atlantic multidecadal oscillation (AMO) has an important influence on this interdecadal shift. During 1998–2016, the AMO was in a positive phase (+AMO), meaning warmer sea surface temperature anomalies (SSTA) in the North Atlantic, which could lift the geopotential height and cause anticyclonic circulations over the basin. Through the cyclonic–anticyclonic circulation alternating teleconnection wave train over Eurasia, the atmospheric system over the North Atlantic could induce cyclonic circulations and reduce the geopotential heights over CA, that is, weaken the high pressure at the upper level, which is not conducive to warming and EHTs in CA. For the −AMO period (1983–1997), due to the similar atmospheric response mechanism, the negative SSTA in the North Atlantic and the wave train with reversed anomaly centres can be found, causing anticyclonic circulations and rising geopotential heights over CA. The high pressure at the upper level in CA would be strengthened, leading to favourable EHT conditions. Overall, we conclude that the current AMO (+AMO) has a mitigating role on the EHTs of CA, and the findings also emphasize that if the future AMO shifts to a negative phase, the EHTs of CA may worsen than at present.

A Regional Air‐Sea Coupled Model Developed for the East Asia and Western North Pacific Monsoon Region

AbstractIn this study, we developed a regional coupled model for the western North Pacific (WNP) and East Asian region. The atmospheric/oceanic component of the coupled model was the Weather Research and Forecasting and the Regional Ocean Modeling System, coupled through the National Center for Atmospheric Research Coupler version 7 (CPL7). An evaluation is provided through the simulation of the climatology and interannual variability of the summer monsoon climate from 1982 to 2015. The coupled model is also compared with a solely atmospheric run, which is driven by the observed sea surface temperature (SST) as the surface boundary. The results show that the coupled model has good capability in modeling the climate in the WNP and East Asian domain, including the climatology of summer precipitation and circulation, the subseasonal (month‐to‐month) variation in the western Pacific subtropical high and associated precipitation, and the seasonal cycle of the East Asian rain belt. One merit of this model is its ability to simulate the northward and eastward shift from early to late summer. With respect to the interannual variability, the model captures the spatial pattern of the leading mode of summer precipitation, with a north–south dipole mode in the studied region. The model also reproduces the larger SST variability in the northern part of this region. The temporal correlation coefficient between the coupled simulation and observation was 0.70 for the precipitation and 0.53 for the SST leading mode. The coupled model also captures the precipitation–SST relationship, which results from reasonably considering the air–sea coupling processes in the coupled run.

A One-Dimensional Blocking Index Becomes Two-Dimensional Using GIS Technology

Many previous studies of the occurrence of blocking anticyclones, their characteristics, and dynamics have defined the onset longitude using the one-dimensional zonal index type criterion proposed by Lejenas and Okland. In addition to examining the blocking event itself, the onset longitude was determined to start at the nearest five degrees longitude using the National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalyses that were used to identify the events. In this study, each blocking event in the University of Missouri Blocking Archive was re-examined to identify an onset latitude, and this information was added to the archive. The events were then plotted and displayed on a map of the Northern or Southern Hemisphere using Geographic Information System (GIS) software housed at the University of Missouri as different colored and sized dots according to block intensity and duration, respectively. This allowed for a comparison of blocking events in the archive above to studies that used a two-dimensional index. Then the common onset regions were divided by phase of the El Nino and Southern Oscillation (ENSO), and the typical onset of intense and persistent blocking events could be examined. The results found a favorable comparison between the onset regions identified here and those found in previous studies that used a two-dimensional blocking index. Additionally, there was variability identified in the onset regions of blocking in both hemispheres by ENSO phase, including the location of more intense and persistent events.

Performance Estimation and System Modeling for Refractive Index Structure Constant Cn2

Random turbulence fluctuations cause continuous fluctuations in the refractive index, which will eliminate the coherence of light waves. Research into atmospheric turbulence is in fact an investigation of the atmospheric refractive index. The constant of atmospheric structure represents a significant parameter that is indicative of the strength of the atmospheric turbulence. In the present study, the performance of some standard models, such as Hufnagel-Valley 5/7, Sub-mission Laser Communication, Critical Laser Enhancing Atmospheric Research, and the Air Force Geophysics Laboratory and Air Force Maui Optical Station, for estimating the, was evaluated with a focus on location assessment. The bias and RMSE were found to be significantly less than 1x10-14 m^-2/3 for Holloman and Hefei cities, and σ is basically less than 0.25x10-14 m^-2/3 for Holloman and Hefei cities. During day and night transitions, Rxy, is well for Holloman, Louisiana, and Hefei cities. Using standard models, we discovered a satisfactory match between the measured (observed) and estimated values for tropical locations.

Effects of Forcing Uncertainties on the Thermospheric and Ionospheric States During Geomagnetic Storm and Quiet Periods

AbstractUpper‐atmospheric weather prediction is subject to various types of forcing uncertainties. Understanding the sensitivity of the thermosphere and ionosphere to forcing uncertainties under different geomagnetic conditions is critical for space weather predictions. Ensemble simulations of a whole atmospheric model, the National Center for Atmospheric Research Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (WACCM‐X), with various kinds of forcing perturbation is used to evaluate the upper atmosphere's response to the uncertainties of different forcings. Two kinds of forcing uncertainties are addressed: the lower atmospheric wave and tide forcing uncertainties and high‐latitude electric potential uncertainty. These uncertainties are estimated in different ways and applied to generate forcing perturbations in the WACCM‐X. WACCM‐X can simulate the upper atmosphere's response to the uncertainties of the lower atmospheric wave and tide forcings related to different lower atmospheric conditions. High‐latitude electric potential uncertainty is estimated based on the SuperMag and SuperDARN data through the Assimilative Mapping of Geospace Observations, which is applied to generate the forcing perturbation of high‐latitude electric potential in the WACCM‐X. The results show that the impact of high‐latitude electric potential uncertainty is significant globally during the 2013 St. Patrick's Day storm. The lower atmospheric wave and tide forcing uncertainties result in a global impact on the upper atmosphere in the model. The sensitivity of the upper atmosphere to both uncertainties is approximately the combination of the two individually, though the combined effects are not a linear sum, indicating non‐linearities in the ionosphere and thermosphere response to forcing uncertainties.

Atmospheric Convection Research Using Autonomous Surface Vehicles

Under the international field program Years of the Maritime Continent (YMC), we conducted a field campaign YMC-Boreal Summer Monsoon study in 2020 (YMC-BSM 2020) in the tropical western Pacific in August - September 2020. While this campaign was aimed to capture and understand the behavior of northward propagating boreal summer intraseasonal oscillation by forming an observation array with a ship and three islands, we also deployed three autonomous surface vehicles (ASVs) and one surface buoy around the research vessel Mirai for one month. The latter was designed not only to study air-sea interaction but also to extend a capability of ASVs for meso-scale atmospheric convection research in future. Thus, in this article we demonstrate that deployment of several instrumented ASVs can capture some basic atmospheric features associated with convection development by showing several comparisons with that obtained by other measurements. Deploying several ASVs in order of 100 km scale is the key, because it can capture gradients of surface atmospheric and oceanic parameters such as sea surface temperatures and can demonstrate a relation between their gradients and atmospheric convection-related features. Since ASVs can be deployed from small islands and controlled remotely to occupy any designated area, this might engage future use of ASVs to study atmospheric convection more flexibly.

TEC and ROTI Measurements from a New GPS Receiver at BOWEN University, Nigeria

Scintillation and total electron content (TEC) are the two major examples of the top-side ionospheric parameters that are recorded differently by most Global Positioning System (GPS) receivers. The new GPS sensor created by the Atmospheric and Space Technology Research Associates (ASTRA), Cornell University, and the University of Texas, Austin have capability to record scintillation and TEC fluctuations simultaneously. Hence, the Connected Autonomous Space Environment Sensor (CASES) from ASTRA is a software-defined GPS receiver with the dual frequency of L1 C/A and L2C codes for space-weather monitoring and can be remotely programmed via an internet source. The receiver employs numerous novel techniques that make it suitable for space-weather studies compared to other nearby GPS receivers, such as different methods for eliminating local clock effects, an advanced triggering mechanism for determining scintillation onset, data buffering to permit observation of the prelude to scintillation, and data-bit prediction and wipe-off for robust tracking. Moreover, the CASES hardware is made up of a custom-built dual frequency, a digital signal processor board, and a “single board computer” with an ARM microcontroller. We have used the CASES GPS receiver newly installed at Bowen University, Iwo, Nigeria, to investigate the TEC and the rate of the TEC index (ROTI) around the equatorial region. Measurements of the TEC and ROTI showed similar variation trends in monthly, seasonal, and annual periods when compared to TEC and ROTI measurements from a nearby station, BJCO at Cotonou, Benin Republic. The newly installed GPS receiver looks promising for scientific use as it is the only one operational in Nigeria at the moment.

Characterization of the middle and upper atmosphere temperatures by Rayleigh scattering Lidar

The temperature plays a critical role in atmospheric research. A measurement system based on Rayleigh scattering Lidar was developed in this study to detect mid and upper-level atmospheric temperature. To analyze the error introduced by the calibration point temperature, the echo signal was simulated. The continuously measured atmospheric temperature structure is stable. The measured atmospheric temperature profile follows the same trend as the atmospheric mode, as shown by comparison with different modes and balloons. The mean difference between the measured atmospheric temperature and the balloon temperature is 2.59 K, with the error mostly concentrated below 5 K. Continuous observation of atmospheric temperature using the system revealed the occurrence of temperature-induced gravity waves at a vertical wavelength from 2 to 3 km at an altitude between 30 and 45 m. Partial fragmentation occurs when energy dissipation is performed in the low-frequency mode from 38 to 45 km. This system was demonstrated to effectively detect temperature and continuously observe gravity waves, with its accuracy confirmed by comparison with balloon temperature measurements.

The dependence of aerosols' global and local precipitation impacts on the emitting region

Abstract. The influence of the geographic distribution of aerosol emissions on the magnitude and spatial pattern of their precipitation impacts remains poorly understood. In this study, the global climate model NCAR CESM1 (National Center for Atmospheric Research Community Earth System Model version 1.2) is used in coupled atmosphere–slab ocean mode to simulate the global hydrological-cycle response to a fixed amount and composition of aerosol emitted from eight key source regions. The results indicate that the location of aerosol emissions is a strong determinant of both the magnitude and spatial distribution of the hydrological response. The global-mean precipitation response to aerosol emissions is found to vary over a 6-fold range depending solely on source location. Mid-latitude sources generate larger global-mean precipitation responses than do tropical and sub-tropical sources, driven largely by the former's stronger global-mean temperature influence. However, the spatial distribution of precipitation responses to some (largely tropical and sub-tropical) regional emissions is almost entirely localized within the source region, while responses to other (primarily mid-latitude) regional emissions are almost entirely remote. It is proposed that this diversity arises from the differing strength with which each region's emissions generate fast precipitation responses that remain largely localized. The findings highlight that tropical regions are particularly susceptible to hydrological-cycle change from either local or remote aerosol emissions, encourage greater investigation of the processes controlling localization of the precipitation response to regional aerosols, and demonstrate that the geographic distribution of anthropogenic aerosol emissions must be considered when estimating their hydrological impacts.