scholarly journals Evaluating the Lower Tropospheric COSMIC GPS Radio Occultation Sounding Quality over the Arctic

2017 ◽  
Author(s):  
Xiao Yu ◽  
Feiqin Xie ◽  
Chi O. Ao
Keyword(s):  
Data Processing ◽  
Radio Occultation ◽  
Lower Troposphere ◽  
Parametric Uncertainty ◽  
Ocean Surface ◽  
Specific Humidity ◽  
The Arctic ◽  
Near Surface ◽  
High Vertical Resolution ◽  
Active Research

Abstract. Lower tropospheric moisture and temperature measurements are crucial for understanding weather predication and climate change. Global Positioning System radio occultation (GPS RO) has been demonstrated as a high-quality observation with high-vertical-resolution and sub-Kelvin temperature precision from the upper troposphere to the stratosphere. In the tropical lower troposphere, particularly the lowest 2 km, the quality of RO retrievals is known to be degraded and is a topic of active research. However, it is not clear whether similar problems exist in the high latitudes, particularly over the Artic, which is characterized by smooth ocean surface and often negligible moisture in the atmosphere. In this study, three-year (2008–2010) GPS RO soundings from COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) over the Arctic (65° N-90° N) show uniform spatial sampling with average penetration depth within 300 m above the ocean surface. Over 70 % soundings penetrate below 300 m in all non-summer seasons but only about 50–60 % in summer, when near-surface moisture and its variation increase. Both structural and parametric uncertainties of GPS RO soundings were also analyzed. The structural uncertainty (due to different data processing approaches) is estimated to be within 0.07 % in refractivity, 0.72 K in temperature and −0.029 g/kg in specific humidity below 10 km, which is derived by comparing RO retrievals from two independent data processing centers. The parametric uncertainty (internal uncertainty of RO sounding) is quantified by comparing GPS RO with near-coincident radiosonde and ECMWF ERA-Interim profiles. A systematic negative bias up to ~ 1 % in refractivity below 2 km is only seen in the summer, which confirms the moisture impact on GPS RO quality.

scholarly journals Evaluating the lower-tropospheric COSMIC GPS radio occultation sounding quality over the Arctic

2018 ◽  
Vol 11 (4) ◽  
pp. 2051-2066 ◽  
Author(s):  
Xiao Yu ◽  
Feiqin Xie ◽  
Chi O. Ao
Keyword(s):  
Data Processing ◽  
Radio Occultation ◽  
Weather Prediction ◽  
Lower Troposphere ◽  
Parametric Uncertainty ◽  
Ocean Surface ◽  
Specific Humidity ◽  
The Arctic ◽  
Near Surface ◽  
Active Research

Abstract. Lower-tropospheric moisture and temperature measurements are crucial for understanding weather prediction and climate change. Global Positioning System radio occultation (GPS RO) has been demonstrated as a high-quality observation technique with high vertical resolution and sub-kelvin temperature precision from the upper troposphere to the stratosphere. In the tropical lower troposphere, particularly the lowest 2 km, the quality of RO retrievals is known to be degraded and is a topic of active research. However, it is not clear whether similar problems exist at high latitudes, particularly over the Arctic, which is characterized by smooth ocean surface and often negligible moisture in the atmosphere. In this study, 3-year (2008–2010) GPS RO soundings from COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) over the Arctic (65–90° N) show uniform spatial sampling with average penetration depth within 300 m above the ocean surface. Over 70 % of RO soundings penetrate deep into the lowest 300 m of the troposphere in all non-summer seasons. However, the fraction of such deeply penetrating profiles reduces to only about 50–60 % in summer, when near-surface moisture and its variation increase. Both structural and parametric uncertainties of GPS RO soundings were also analyzed. The structural uncertainty (due to different data processing approaches) is estimated to be within  ∼  0.07 % in refractivity,  ∼  0.72 K in temperature, and  ∼  0.05 g kg−1 in specific humidity below 10 km, which is derived by comparing RO retrievals from two independent data processing centers. The parametric uncertainty (internal uncertainty of RO sounding) is quantified by comparing GPS RO with near-coincident radiosonde and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim profiles. A systematic negative bias up to  ∼  1 % in refractivity below 2 km is only seen in the summer, which confirms the moisture impact on GPS RO quality.

scholarly journals Global 3D Features of Error Variances of GPS Radio Occultation and Radiosonde Observations

2020 ◽  
Vol 13 (1) ◽  
pp. 1
Author(s):  
Xu Xu ◽  
Xiaolei Zou
Keyword(s):  
Radio Occultation ◽  
Weather Prediction ◽  
Lower Troposphere ◽  
Error Variance ◽  
Specific Humidity ◽  
Temperature Error ◽  
Observation Error ◽  
Bending Angle ◽  
Gps Radio Occultation ◽  
Low Latitudes

Global Positioning System (GPS) radio occultation (RO) and radiosonde (RS) observations are two major types of observations assimilated in numerical weather prediction (NWP) systems. Observation error variances are required input that determines the weightings given to observations in data assimilation. This study estimates the error variances of global GPS RO refractivity and bending angle and RS temperature and humidity observations at 521 selected RS stations using the three-cornered hat method with additional ERA-Interim reanalysis and Global Forecast System forecast data available from 1 January 2016 to 31 August 2019. The global distributions, of both RO and RS observation error variances, are analyzed in terms of vertical and latitudinal variations. Error variances of RO refractivity and bending angle and RS specific humidity in the lower troposphere, such as at 850 hPa (3.5 km impact height for the bending angle), all increase with decreasing latitude. The error variances of RO refractivity and bending angle and RS specific humidity can reach about 30 N-unit2, 3 × 10−6 rad2, and 2 (g kg−1)2, respectively. There is also a good symmetry of the error variances of both RO refractivity and bending angle with respect to the equator between the Northern and Southern Hemispheres at all vertical levels. In this study, we provide the mean error variances of refractivity and bending angle in every 5°-latitude band between the equator and 60°N, as well as every interval of 10 hPa pressure or 0.2 km impact height. The RS temperature error variance distribution differs from those of refractivity, bending angle, and humidity, which, at low latitudes, are smaller (less than 1 K2) than those in the midlatitudes (more than 3 K2). In the midlatitudes, the RS temperature error variances in North America are larger than those in East Asia and Europe, which may arise from different radiosonde types among the above three regions.

scholarly journals Seasonal Prediction Skill of Northern Extratropical Surface Temperature Driven by the Stratosphere

2017 ◽  
Vol 30 (12) ◽  
pp. 4463-4475 ◽  
Author(s):  
Liwei Jia ◽  
Xiaosong Yang ◽  
Gabriel Vecchi ◽  
Richard Gudgel ◽  
Thomas Delworth ◽  
...  
Keyword(s):  
Climate Model ◽  
Lower Troposphere ◽  
Polar Vortex ◽  
Seasonal Prediction ◽  
The Arctic ◽  
Northern Eurasia ◽  
Stratospheric Polar Vortex ◽  
Near Surface ◽  
Predictive Skill

This study explores the role of the stratosphere as a source of seasonal predictability of surface climate over Northern Hemisphere extratropics both in the observations and climate model predictions. A suite of numerical experiments, including climate simulations and retrospective forecasts, are set up to isolate the role of the stratosphere in seasonal predictive skill of extratropical near-surface land temperature. It is shown that most of the lead-0-month spring predictive skill of land temperature over extratropics, particularly over northern Eurasia, stems from stratospheric initialization. It is further revealed that this predictive skill of extratropical land temperature arises from skillful prediction of the Arctic Oscillation (AO). The dynamical connection between the stratosphere and troposphere is also demonstrated by the significant correlation between the stratospheric polar vortex and sea level pressure anomalies, as well as the migration of the stratospheric zonal wind anomalies to the lower troposphere.

scholarly journals Climate intercomparison of GPS radio occultation, RS90/92 radiosondes and GRUAN over 2002 to 2013

2014 ◽  
Vol 7 (11) ◽  
pp. 11735-11769
Author(s):  
F. Ladstädter ◽  
A. K. Steiner ◽  
M. Schwärz ◽  
G. Kirchengast
Keyword(s):  
Radio Occultation ◽  
Global Climate ◽  
Time Frame ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Gps Radio Occultation ◽  
Long Term Stability ◽  
High Vertical Resolution ◽  
Global Coverage

Abstract. Observations from the GPS radio occultation (GPSRO) satellite technique and from the newly established GCOS Reference Upper Air Network (GRUAN) are both candidates to serve as reference observations in the Global Climate Observing System (GCOS). Such reference observations are key to decrease existing uncertainties in upper-air climate research. There are now more than 12 years of data available from GPSRO, with the recognized properties high accuracy, global coverage, high vertical resolution, and long-term stability. These properties make GPSRO a suitable choice for comparison studies with other upper-air observational systems. The GRUAN network consists of reference radiosonde ground stations (16 at present), which adhere to the GCOS climate monitoring principles. In this study, we intercompare GPSRO temperature and humidity profiles and Vaisala RS90/92 data from the "standard" global radiosonde network over the whole 2002 to 2013 time frame. Additionally, we include the first years of GRUAN data (using Vaisala RS92), available since 2009. GPSRO profiles which occur within 3 h and 300 km of radiosonde launches are used. Very good agreement is found between all three datasets with temperature differences usually less than 0.2 K. In the stratosphere above 30 hPa, temperature differences are larger but still within 0.5 K. Day/night comparisons with GRUAN data reveal small deviations likely related to a warm bias of the radiosonde data at high altitudes, but also residual errors from the GPSRO retrieval process might play a role. Vaisala RS90/92 specific humidity exhibits a dry bias of up to 40% in the upper troposphere, with a smaller bias at lower altitudes within 15%. GRUAN shows a marked improvement in the bias characteristics, with less than 5% difference to GPSRO up to 300 hPa. GPSRO dry temperature and physical temperature are validated using radiosonde data as reference. We find that GPSRO provides valuable long-term stable reference observations with well-defined error characteristics for climate applications and for anchoring other upper-air measurements.

scholarly journals In-situ sounding of radiation flux profiles through the Arctic lower troposphere

2018 ◽  
Author(s):  
Ralf Becker ◽  
Marion Maturilli ◽  
Rolf Philipona ◽  
Klaus Behrens
Keyword(s):  
Surface Composition ◽  
Lower Troposphere ◽  
Time Frame ◽  
The Arctic ◽  
Heating Rates ◽  
Heterogeneous Terrain ◽  
Near Surface ◽  
Clear Sky ◽  
Radiation Fluxes

Abstract. In-situ profiles of all four net radiation components were obtained at Ny Ålesund/Svalbard (78.9° N, 11.9° E) in the time frame May 04–21, 2015. Measurements could be performed using adapted high quality instrumentation classified as secondary standard carried by a tethered balloon system. Balloon lifted measurements of albedo under clear sky conditions demonstrate the altitude dependence of this parameter over heterogeneous terrain. Depending on the surface composition within the sensor's footprint, the albedo over predominantly snow covered surfaces was found to decrease to 53.4 % and 35.8 % compared to 73.1 % and 78.8 % measured with near surface references, respectively. Albedo profiles show an all-sky maximum at 150 m above surface level, and an averaged vertical change rate of −2.1 %/100 m (clear sky) and −3.4 %/100 m (overcast) above. Profiling of arctic low-level clouds reveals distinct vertical gradients in all radiation fluxes but longwave upward. Observed radiative cooling at cloud top with heating rates of −53 to −84 K/d in subsequent observations tend to be lower than suggested by 1-D simulations.

Modulation of PDO in the Arctic tropospheric warming

2020 ◽  
Author(s):  
Lingling Suo ◽  
Yongqi Gao ◽  
Guillaume Gastineau ◽  
Yu-Chiao Liang ◽  
Rohit Ghosh ◽  
...  
Keyword(s):  
Model Simulation ◽  
Winter Season ◽  
Lower Troposphere ◽  
Warming Trend ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Joint Analysis ◽  
Near Surface ◽  
Arctic Warming ◽  
Surface Warming

<p>The Arctic amplified warming under global warming is one of the prominent climate change events during the past several decades. Arctic sea ice retreat contributed the majority of the near-surface warming, and little to the mid-troposphere warming. The remote factors might contribute to or modulate the aloft Arctic warming.</p><p>Here we performed a multi-model joint-analysis to study the role of the Pacific decadal oscillation, which is one of the most important recurring ocean-atmosphere variability in the climate system, in the tropospheric Arctic warming. In the multi-model simulation, PDO reduced the Arctic warming trend during 1979-2013 significantly in spring, Autumn and early winter season from the near-surface to the upper troposphere. The reduction of warming reaches 0.3 / 0.2 °C per decade in the upper / lower troposphere.</p>

scholarly journals The Intraseasonal and Interannual Variability of Arctic Temperature and Specific Humidity Inversions

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 214 ◽  
Author(s):  
Lejiang Yu ◽  
Qinghua Yang ◽  
Mingyu Zhou ◽  
Xubin Zeng ◽  
Donald H. Lenschow ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Intraseasonal Variability ◽  
Intraseasonal Oscillation ◽  
Lower Troposphere ◽  
Specific Humidity ◽  
The Arctic ◽  
Self Organizing Map ◽  
Eastern Hemisphere ◽  
Temperature And Humidity ◽  
Arctic Temperature

Temperature and humidity inversions are common in the Arctic’s lower troposphere, and are a crucial component of the Arctic’s climate system. In this study, we quantify the intraseasonal oscillation of Arctic temperature and specific humidity inversions and investigate its interannual variability using data from the Surface Heat Balance of the Arctic (SHEBA) experiment from October 1997 to September 1998 and the European Centre for Medium-Range Forecasts (ECMWF) Reanalysis (ERA)-interim for the 1979–2017 period. In January 1998, there were two noticeable elevated inversions and one surface inversion. The transitions between elevated and surface-based inversions were associated with the intraseasonal variability of the temperature and humidity differences between 850 and 950 hPa. The self-organizing map (SOM) technique is utilized to obtain the main modes of surface and elevated temperature and humidity inversions on intraseasonal time scales. Low (high) pressure and more (less) cloud cover are related to elevated (surface) temperature and humidity inversions. The frequency of strong (weak) elevated inversions over the eastern hemisphere has decreased (increased) in the past three decades. The wintertime Arctic Oscillation (AO) and Arctic Dipole (AD) during their positive phases have a significant effect on the occurrence of surface and elevated inversions for two Nodes only.

scholarly journals Evaluation of Arctic cloud products from the EUMETSAT Climate Monitoring Satellite Application Facility based on CALIPSO-CALIOP observations

2009 ◽  
Vol 9 (4) ◽  
pp. 16755-16810 ◽  
Author(s):  
K.-G. Karlsson ◽  
A. Dybbroe
Keyword(s):  
Weather Prediction ◽  
Lower Troposphere ◽  
Arctic Region ◽  
Numerical Weather Prediction Model ◽  
The Arctic ◽  
Cloud Type ◽  
Near Surface ◽  
Noaa Avhrr ◽  
Climate Monitoring ◽  
June July

Abstract. The performance of the three cloud products cloud fractional cover, cloud type and cloud top height, derived from NOAA AVHRR data and produced by the EUMETSAT Climate Monitoring Satellite Application Facility, has been evaluated in detail over the Arctic region for four months in 2007 using CALIPSO-CALIOP observations. The evaluation was based on 142 selected NOAA/Metop overpasses allowing almost 400 000 individual matchups between AVHRR pixels and CALIOP measurements distributed approximately equally over the studied months (June, July, August and December 2007). Results suggest that estimations of cloud amounts are very accurate during the polar summer season while a substantial loss of detected clouds occurs in the polar winter. Evaluation results for cloud type and cloud top products point at specific problems related to the existence of near isothermal conditions in the lower troposphere in the polar summer and the use of reference vertical temperature profiles from Numerical Weather Prediction model analyses. The latter are currently not detailed enough in describing true conditions relevant on the pixel scale. This concerns especially the description of near-surface temperature inversions which are often too weak leading to large errors in interpreted cloud top heights.

scholarly journals Evaluating Arctic clouds modelled with the Unified Model and Integrated Forecasting System

2021 ◽  
Author(s):  
Gillian Young ◽  
Jutta Vüllers ◽  
Peggy Achtert ◽  
Paul Field ◽  
Jonathan J. Day ◽  
...  
Keyword(s):  
Water Content ◽  
Lower Troposphere ◽  
Unified Model ◽  
The Arctic ◽  
Near Surface ◽  
Arctic Clouds ◽  
Thermodynamic Structure ◽  
Driving Model ◽  
Double Moment ◽  
Forecasting System

Abstract. By synthesising remote-sensing measurements made in the central Arctic into a model-gridded Cloudnet cloud product, we evaluate how well the Met Office Unified Model (UM) and European Centre for Medium-Range Weather Forecasting Integrated Forecasting System (IFS) capture Arctic clouds and their associated interactions with the surface energy balance and the thermodynamic structure of the lower troposphere. This evaluation was conducted using a four-week observation period from the Arctic Ocean 2018 expedition, where the transition from sea ice melting to freezing conditions was measured. Three different cloud schemes were tested within a nested limited area model (LAM) configuration of the UM – two regionally-operational single-moment schemes (UM_RA2M and UM_RA2T), and one novel double-moment scheme (UM_CASIM-100) – while one global simulation was conducted with the IFS, utilising its default cloud scheme (ECMWF_IFS). Consistent weaknesses were identified across both models, with both the UM and IFS overestimating cloud occurrence below 3 km. This overestimation was also consistent across the three cloud configurations used within the UM framework, with > 90 % mean cloud occurrence simulated between 0.15 and 1 km in all model simulations. However, the cloud microphysical structure, on average, was modelled reasonably well in each simulation, with the cloud liquid water content (LWC) and ice water content (IWC) comparing well with observations over much of the vertical profile. The key microphysical discrepancy between the models and observations was in the LWC between 1 and 3 km, where most simulations (all except UM_RA2T) overestimated the observed LWC. Despite this reasonable performance in cloud physical structure, both models failed to adequately capture cloud-free episodes: this consistency in cloud cover likely contributes to the ever-present near-surface temperature bias simulated in every simulation. Both models also consistently exhibited temperature and moisture biases below 3 km, with particularly strong cold biases coinciding with the overabundant modelled cloud layers. These biases are likely due to too much cloud top radiative cooling from these persistent modelled cloud layers and were interestingly consistent across the three UM configurations tested, despite differences in their parameterisations of cloud on a sub-grid-scale. Alarmingly, our findings suggest that these biases in the regional model were inherited from the driving model, thus triggering too much cloud formation within the lower troposphere. Using representative cloud condensation nuclei concentrations in our double-moment UM configuration, while improving cloud microphysical structure, does little to alleviate these biases; therefore, no matter how comprehensive we make the cloud physics in the nested LAM configuration used here, its cloud and thermodynamic structure will continue to be overwhelmingly biased by the meteorological conditions of its driving model.

Isle of Man, Galapagos and sunspot data show net cooling hid double exponential ocean warming danger: +3°C in 2014, +4°C likely by 2016.

2015 ◽  
Vol 9 (2) ◽  
pp. 2355-2371
Author(s):  
Dr J Brian Matthews
Keyword(s):  
Global Warming ◽  
Ocean Surface ◽  
Ocean Warming ◽  
The Arctic ◽  
Variable Boundary ◽  
Temperature Function ◽  
Near Surface ◽  
Isle Of Man ◽  
Surface Data ◽  
Double Exponential

Anthropogenic global warming (AGW) heat is trapped by the greenhouse gas (GHG) blanket, and the ocean surface layer. It is 93% in the ocean and drives atmospheric warming. The 111-year mean daily surface temperatures are 10.5±0.5°C at Port Erin (PE) Isle of Man compared with 9.6±4.8°C in Central England (CET) air. The Port Erin 5½-year max-min heat cycle synchronizes to the 11-year solar heat pump sunspot cycle. Tropical heat arrives 2 years after a solar maximum on wind-driven currents in the stratified sea surface. Runoff from bottom-up melted Arctic icesheets arrives 3½ year later at solar minimum. These warm and cold waters are the biodiversity source. PE is unique with seasonal meltwaters of Pacific and Atlantic origin. The North Pacific warms twice as fast as other oceans. All ocean near-surface gyre currents harmonize with sunspot cycles. Net cooling by polar icemelt masks catastrophic exponential ocean warming and icemelt. Eleven counter-rotating surface gyres carry heat and nutrients globally in verified ocean surface circulation system.Exponential growth is unsustainable in a finite system. It trends to infinity. Double-exponential gets there twice as quickly. The GHG blanket, grown double-exponentially for 250 years, is now in control. Ocean heat absorption takes 150-250 years. Arctic icemelt increases double-exponentially. The Arctic long-term annual freeze-melt volume cycle is 16.8±1.3 thousand cubic km per year. Polar land icemelt adds ~500 km3 per year. Freeze-brine of salinity >40‰ and temperature –1°C, sinks to the bottom. Equatorial evaporative-brine of salinity >36.4‰ and >28°C floats subsurface under fresh warm layers thickening westwards in tropical meridional cells to ~75m depth. This is consistent with observed extreme weather.Heat imbalance forced Pacific Ocean temperatures above proposed limits of +2°C in 1993, to +3°C in 2014, and is on track for +4°C for 2016. Century-long daily records confirm processes ongoing for 300 years. Coast locations are where impacts are felt and real-time data collected. Corporate governance degraded physics teaching in only 60 years. Individual discovery and data collection was lost. Big science is unnecessary. Satellites cannot do plankton tows. Computer models are governed by the rule of ‘garbage-in garbage-out’. They must be verified by in situ data that cannot be collected retrospectively. Continuous timeseries surface profile data from fixed ocean station locations on a global variable-boundary network are essential. Scientists, if well-trained in ocean experimental physics, can do the hard work.Time-poor scientists, stripped of their intellectual property rights, under rewarded, poorly educated, and ruthlessly exploited by growth-obsessed commercial interests, missed catastrophic global warming and multiple extreme consequences. Climate scientists abandoned classical physics and Newton-Hooke field verification in favor of unverified beliefs, models, and apps. Climate studies confuse heat with temperature, do not include basal icemelt, density temperature-salinity function, Clausius-Clapeyron evaporation exponential skin temperature function, asymmetric brine-heat sequestration, solar and tidal pumping, infra-red GHG heat trap, vertical tropical cells, freshwater warm pools; or wind-driven surface currents at 3 percent of windspeed. Climate model mistaken assumptions lead to the absurd conclusion that evaporation in the Labrador Sea at midnight in midwinter is greater than at the midday Equator.The Isle of Man provides an ideal location for continued monitoring and mitigation research, teaching and public service in a dedicated non-commercial independent multidisciplinary university-type setting. Quality teaching is the major priority. Commercial monopoly rights need replacement with free, fully open discussions and publications. Quality not quantity should be paramount. Internationally competitive academics should control subservient lower paid support staff.Every day without ocean surface data means vital scientific truth lost of interest and concern to all populations. Predictions are groundless without accurate continuous ocean surface data. Skeptics, politicians, statisticians, those with stakes in the status quo, and established research censors obstructing scientific progress squabble in ignorance while the globe burns.

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