Radiation Anomalies Research Articles

Arctic Sea Ice Growth in Response to Synoptic- and Large-Scale Atmospheric Forcing from CMIP5 Models

AbstractWe explore the response of wintertime Arctic sea ice growth to strong cyclones and to large-scale circulation patterns on the daily scale using Earth system model output in phase 5 of the Coupled Model Intercomparison Project (CMIP5). A combined metrics ranking method selects three CMIP5 models that are successful in reproducing the wintertime Arctic dipole (AD) pattern. A cyclone identification method is applied to select strong cyclones in two subregions in the North Atlantic to examine their different impacts on sea ice growth. The total change of sea ice growth rate (SGR) is split into those respectively driven by the dynamic and thermodynamic atmospheric forcing. Three models reproduce the downward longwave radiation anomalies that generally match thermodynamic SGR anomalies in response to both strong cyclones and large-scale circulation patterns. For large-scale circulation patterns, the negative AD outweighs the positive Arctic Oscillation in thermodynamically inhibiting SGR in both impact area and magnitude. Despite the disagreement on the spatial distribution, the three CMIP5 models agree on the weaker response of dynamic SGR than thermodynamic SGR. As the Arctic warms, the thinner sea ice results in more ice production and smaller spatial heterogeneity of thickness, dampening the SGR response to the dynamic forcing. The higher temperature increases the specific heat of sea ice, thus dampening the SGR response to the thermodynamic forcing. In this way, the atmospheric forcing is projected to contribute less to change daily SGR in the future climate.

Distinct Eurasian climate anomalies associated with strong and weak MJO events

AbstractThe MJO‐related tropical Indian Ocean outgoing longwave radiation anomalies display a bimodal distribution, indicating two types of MJO events. The present study distinguishes 14 strong and 16 weak MJO events during the 37 winters from 1979 to 2016 and compares the circulation and climate over the mid‐latitude Eurasia between strong and weak MJO events. Cold anomalies appear over Siberia and East Asia during strong MJO events when the MJO‐related convection is located over the tropical Indian Ocean, whereas the temperature anomalies are weak over Eurasia during weak MJO events. The cold anomalies over Eurasia in strong MJO events are associated with the development of surface anticyclonic anomalies and the accompanying northerly wind anomalies. On one hand, the enhancement of surface anticyclonic anomalies can be attributed to the poleward Rossby wave packets triggered by the MJO convection over the tropical Indian Ocean. On the other hand, the strong convective heating over the tropical Indian Ocean can induce anomalous meridional overturning circulation between the tropics and mid‐latitudes. The anomalous divergent winds associated with the convective heating can reach western Siberia and the descending branch of the vertical cell contributes to the enhancement of surface anticyclonic anomalies and northerly wind anomalies, leading to cold anomalies over Siberia and East Asia. In weak MJO events, the poleward Rossby waves are weak and anomalous meridional overturning is of limited meridional extent. As a result, the MJO‐related wind anomalies are weak and the associated temperature anomalies are small over large areas of Eurasia.

Identifying the Sources of Continental Summertime Temperature Variance Using a Diagnostic Model of Land–Atmosphere Interactions

AbstractClimate models show that soil moisture and its subseasonal fluctuations have important impacts on the surface latent heat flux, thus regulating surface temperature variations. Using correlations between monthly anomalies in net absorbed radiative fluxes, precipitation, 2-m air temperature, and soil moisture in the ERA-Interim reanalysis and the HadCM3 climate model, we develop a linear diagnostic model to quantify the major effects of land–atmosphere interactions on summertime surface temperature variability. The spatial patterns in 2-m air temperature and soil moisture variance from the diagnostic model are consistent with those from the products from which it was derived, although the diagnostic model generally underpredicts soil moisture variance. We use the diagnostic model to quantify the impact of soil moisture, shortwave radiation, and precipitation anomalies on temperature variance in wet and dry regions. Consistent with other studies, we find that fluctuations in soil moisture amplify temperature variance in dry regions through their impact on latent heat flux, whereas in wet regions temperature variability is muted because of high mean evapotranspiration rates afforded by plentiful surface soil moisture. We demonstrate how the diagnostic model can be used to identify sources of temperature variance bias in climate models.

The Pause End and Major Temperature Impacts during Super El Niños are Due to Shortwave Radiation Anomalies

The hiatus or temperature pause during the 21st century has been the subject of numerous research studies with very different results and proposals. In this study, two simple climate models have been applied to test the causes of global temperature changes. The climate change factors have been shortwave (SW) radiation changes, changes in cloudiness and ENSO (El Niño Southern Oscillation) events assessed as the ONI (Oceanic Niño Index) values and anthropogenic climate drivers. The results show that a simple climate model assuming no positive water feedback follows the satellite temperature changes very well, the mean absolute error (MAE) during the period from 2001 to July 2019 being 0.073°C and 0.082°C in respect to GISTEMP. The IPCC’s simple climate model shows for the same period errors of 0.191°C and 0.128°C respectively. The temperature in 2017-2018 was about 0.2°C above the average value in 2002–2014. The conclusion is that the pause was over after 2014 and the SW anomaly forcing was the major reason for this temperature increase. SW anomalies have had their greatest impacts on the global temperature during very strong (super) El Niño events in 1997-98 and 2015-16, providing a new perspective for ENSO events. A positive SW anomaly continued after 2015-16 which may explain the weak La Niña 2016 temperature impacts, and a negative SW anomaly after 1997-98 may have contributed two strong La Niña peaks 1998-2001. No cause and effect connection could be found between the SW radiation and temperature anomalies in Nino areas.

Tracking of Tropical Intraseasonal Convective Anomalies: 1. Seasonality of the Tropical Intraseasonal Oscillations.

A tracking algorithm based upon a multiple object tracking method is developed to identify, track, and classify Tropical Intraseasonal Oscillations (TISO) on the basis of their direction of propagation. Daily National Oceanic and Atmospheric Administration Outgoing Longwave Radiation anomalies from 1979–2017 are Lanczos band‐pass filtered for the intraseasonal time scale (20–100 days) and spatially averaged with nine neighboring points to get spatially smoothed anomalies over large spatial scales (~105 km2). TISO events are tracked by using a two‐stage Kalman filter predictor‐corrector method. Two dominant components of the TISO (Eastward propagating and Northward propagating) are classified, and it is found that TISO remains active throughout the year. Eastward‐propagating TISO events occur from November to April with a phase speed of ~4 m/s and northward‐propagating TISO events occur from May to October with a phase speed of ~2.5 m/s in both the Indian and Pacific Ocean basins. Composites of the mean background states (wind; sea surface temperature, SST; and moisture) reveal that the co‐occurrence of warm SST and mean westerly zonal wind plays an important role in the direction of propagation and the geographical location of TISO events. In mean state sensitivity experiments with Sp‐CAM4, we have found that the seasonality of TISO in terms of the geographical location of occurrences and direction of propagation is primarily associated with the annual march of the maximum SST and low level zonal wind which tends to follow the SST.

Southern Hemisphere Sensitivity to ENSO Patterns and Intensities: Impacts over Subtropical South America

El Niño flavors influence Subtropical South American (SSA) rainfall through the generation of one or two quasi-stationary Rossby waves. However, it is not yet clear whether the induced wave trains depend on the El Niño pattern and/or its intensity. To investigate this, we performed different sensitivity experiments using an Atmospheric General Circulation Model (AGCM) which was forced considering separately the Canonical and the El Niño Modoki patterns with sea surface temperature (SST) maximum anomalies of 1 and 3 °C. Experiments with 3 °C show that the Canonical El Niño induces two Rossby wave trains, a large one emanating from the western subtropical Pacific and a shorter one initiated over the central-eastern subtropical South Pacific. Only the shorter wave plays a role in generating negative outgoing longwave radiation (OLR) anomalies over SSA. On the other hand, 3 °C El Niño Modoki experiments show the generation of a large Rossby wave train that emanates from the subtropical western south Pacific and reaches South America (SA), promoting the development of negative OLR anomalies over SSA. Experiments with 1 °C show no impacts on OLR anomalies over SSA associated with El Niño Modoki. However, for the Canonical El Niño case there is a statistically significant reduction of the OLR anomalies over SSA related to the intensification of the upper level jet stream over the region. Finally, our model results suggest that SSA is more sensitive to the Canonical El Niño, although this result may be model dependent.

Microwave Brightness Temperature Characteristics of Three Strong Earthquakes in Sichuan Province, China

Passive microwave remote sensing technology is an effective means to identify the thermal anomalies associated with earthquakes due to its penetrating capability through clouds compared with infrared sensors. However, observed microwave brightness temperature is strongly influenced by soil moisture and other surface parameters. In the present article, the segmented threshold method has been proposed to detect anomalous microwave brightness temperature associated with the strong earthquakes occurred in Sichuan province, China, an earthquake-prone area with high soil moisture. The index of microwave radiation anomaly (IMRA) computed by the proposed method is found to enhance prior to the three strong earthquakes, 2008 Wenchuan ( M = 7.8), 2013 Lushan ( M = 6.6), and 2017 Jiuzhaigou ( M = 6.5), occurred during 2008–2018 using the Defense Meteorological Space Program Special Sensor Microwave Imager/Sounder F17 satellite data. Our results show that the microwave brightness temperature anomalies appeared about two months prior to the three strong earthquakes. For the Wenchuan and Lushan earthquakes, the enhanced IMRA distributed along the main fault, which is consistent with the variations of our earlier studies of the 1997 Manyi ( M = 7.5) and the 2001 Kokoxili ( M = 7.8) earthquakes in the region with low soil moisture. For the Jiuzhaigou earthquake, the anomalies distributed around the epicenter and do not indicate the seismogenic structure, which could be due to the presence of a blind fault. It should be noted that quantitative evaluation of IMRA is limited due to infrequent occurrence of earthquakes.

Dawn Spacecraft Performance: Resource Utilization and Environmental Effects During an 11-Year Mission

Dawn was a deep space science mission to the asteroid belt, using solar electric propulsion and a spacecraft derived from an earth-orbiting communications satellite. Although much of the operational history of the mission has been captured in the literature, this work is intended to gather and highlight underreported issues and lessons that would be of specific interest to future electric propulsion and/or asteroid missions. This paper describes the most significant engineering resources consumed over the course of the mission and the use of redundant hardware and software. Also detailed are thermal, micrometeoroid, radiation, and other environmental effects and anomalies that the Dawn spacecraft experienced. A brief description of the mission and spacecraft hardware is also provided.

What Drives the North Atlantic Oscillation’s Temperature Anomaly Pattern? Part II: A Decomposition of the Surface Downward Longwave Radiation Anomalies

AbstractRadiative transfer calculations are conducted to determine the contribution of temperature and water vapor anomalies toward the surface clear-sky downward longwave radiation (DLR) anomalies of the NAO. These calculations are motivated by the finding that the NAO’s skin temperature anomalies are driven primarily by changes in surface DLR. The clear-sky radiative transfer calculations follow the result that the clear-sky surface DLR anomalies can account for most of the all-sky surface DLR anomalies of the NAO. The results of the radiative transfer calculations prompt an analysis of the thermodynamic energy and total column water (TCW) budget equations, as water vapor and temperature anomalies are found to be equally important drivers of the surface DLR anomalies of the NAO. Composite analysis of the thermodynamic energy equation reveals that the temperature anomalies of the NAO are wind driven: the advection of climatological temperature by the anomalous wind drives the NAO’s temperature anomalies at all levels except for those in the upper troposphere–lower stratosphere where the advection of anomalous temperature by the climatological wind becomes dominant. A similar analysis of the TCW budget reveals that changes in TCW are driven by water flux convergence. In addition to determining the drivers of the temperature and TCW anomalies, the thermodynamic energy and water budget analyses reveal that the decay of the temperature anomalies occurs primarily through vertical mixing, and that of the water anomalies mostly by evaporation minus precipitation.

Comments on the paper “Two independent real-time precursors of the 7.8 M earthquake in Ecuador based on radioactive and geodetic processes – Powerful tools for an early warning system” by Toulkeridis et al. (2019)

In the paper entitled “Two independent real-time precursors of the 7.8 M earthquake in Ecuador based on radioactive and geodetic processes – Powerful tools for an early warning system”, Toulkeridis et al. (2019) claim that they found radiation and GPS signal anomalies before the April 16th 2016 Pedernales earthquake (Ecuador) and that their findings can be used to forecast earthquakes in the medium and short term in active continental margins. Using an extended data set that overlaps Toulkeridis et al. (2019) study period, we find: (1) the success rate of predicting earthquakes using radiation anomalies is 2.5 %; (2) radiation anomalies, including the one recorded during the hours before the M 7.8 earthquake, temporally correlate with local rainfall; (3) Toulkeridis et al. (2019) GPS results are physically unrealistic and inconsistent with previously published GPS and InSAR analysis; (4) there is no anomaly in the GPS time series before the earthquake. Therefore, Toulkeridis et al. (2019) results are not reliable evidence of precursors to the M 7.8 earthquake in 2016 in Ecuador, and their proposed method cannot be used to forecast earthquakes.

Impact of rainfall extremes on energy exchange and surface temperature anomalies across biomes in the Horn of Africa

Precipitation extremes have a strong influence on the exchange of energy and water between the land surface and the atmosphere. Although the Horn of Africa has faced recurrent drought and flood events in recent decades, it is still unclear how these events impact energy exchange and surface temperature across different ecosystems. Here, we analyzed the impact of precipitation extremes on spectral albedo (total shortwave, visible, and near-infrared (NIR) broadband albedos), energy balance, and surface temperature in four natural vegetation types: forest, savanna, grassland, and shrubland. We used remotely sensed observations of surface biophysical properties and climate from 2001 to 2016. Our results showed that, in forests and savannas, precipitation extremes led to divergent spectral changes in visible and NIR albedos, which cancelled each other limiting shortwave albedo changes. An exception to this pattern was observed in shrublands and grasslands, where both visible and NIR albedo increased during drought events. Given that shrublands and grasslands occupy a large fraction of the Horn of Africa (52%), our results unveil the importance of these ecosystems in driving the magnitude of shortwave radiative forcing in the region. The average regional shortwave radiative forcing during drought events (−0.64 W m−2, SD 0.11) was around twice that of the extreme wet events (0.33 W m−2, SD 0.09). Such shortwave forcing, however, was too small to influence the surface–atmosphere coupling. In contrast, the surface feedback through turbulent flux changes was strong across vegetation types and had a significant (P < 0.05) impact on the surface temperature and net radiation anomalies, except in forests. The strongest energy exchange and surface temperature anomalies were observed over grassland and the smallest over forest, which was shown to be resilient to precipitation extremes. These results suggest that land management activities that support forest preservation, afforestation, and reforestation can help to mitigate the impact of drought through their role in modulating energy fluxes and surface temperature anomalies in the region.

Do we come from a quantum anomaly?

We present a string-based picture of the cosmological evolution in which (CP-violating) gravitational anomalies acting during the inflationary phase of the universe cause the vacuum energy density to “run” with the effective Hubble parameter squared, [Formula: see text], thanks to the axion field of the bosonic string multiplet. This leads to baryogenesis through leptogenesis with massive right-handed neutrinos. The generation of chiral matter after inflation helps in cancelling the anomalies in the observable radiation- and matter-dominated eras. The present era inherits the same “running vacuum” structure triggered during the inflationary time by the axion field. The current dark energy is thus predicted to be mildly dynamical, and dark matter should be made of axions. Paraphrasing Carl Sagan [ https://www.goodreads.com/author/quotes/10538.Carl_Sagan .]: we are all anomalously made from starstuff.

Variation of global diurnal temperature range associated with the Madden-Julian Oscillation

This study examines the impact of the intraseasonal Madden-Julian Oscillation (MJO) on global land surface diurnal temperature range (DTR) using two daily surface air temperature datasets. The results show that the MJO significantly affects DTR over all the continents. The two datasets are highly consistent with each other, suggesting that the results are robust. Significant correlations exist in all seasons over the tropical continents, including Africa, India, southeast Asia, Australia, central America and Amazon. In the extratropics, the correlations change with season. The highest correlations occur in winter for Europe, in winter and spring for China, in autumn for United States, and in summer and winter for Canada. The surface DTR anomalies coincide well with the outgoing longwave radiation (OLR) anomalies at the top of the atmosphere, suggesting that variations of DTR are associated with variations of clouds, which is consistent with the results of previous studies on DTR trend and variability at seasonal to multi-decadal time-scales. The DTR variations are also associated with changes of deep convection, soil moisture and snow cover.

A time-frequency analysis of the thermal radiation background anomalies caused by large earthquakes: A case study of the Wenchuan 8.0 earthquake

Strong earthquakes have an impact on the regional thermal radiation background, which has been both observed and confirmed. This effect produces anomalies in the thermal radiation background (TRBA) and increases the difficulty of extracting a thermal radiation anomaly (TRA) that is associated with an earthquake occurring during the same time period. The extraction and identification of such anomalies has been ignored by previous studies. In this study, we investigate the time-frequency analysis (TFA) method, together with the wavelet filtering of the Daubechies method and the relative power spectrum analysis of the Fourier Welch method to extract and analyse the TRBA caused by the 2008 Wenchuan Ms 8.0 earthquake and the TRA of the 2013 Minxian-Zhangxian Ms 6.6 earthquake using data concerning the brightness temperature of a black body (TBB) from the Fengyun-2 series of geostationary meteorological satellites developed by China. The result showed that this method can effectively extract and analyse the TRBA caused by the Wenchuan earthquake and the TRA of the Minxian-Zhangxian earthquake form a complex background environment. Furthermore, we discussed the impact of the earthquake on the TRBA and segmented the process. The impact is mainly reflected by three aspects; the characteristic period of the TRBA changes, the TRBA occurs at the same time every year, which is identical to the time at which the earthquake anomaly occurred, and the impact process is in stages. We also summarized the correlation between the characteristic parameters of a TRA and the regional thermal radiation background, geography, and climatic factors.

Radiative Control of the Interannual Variability of Arctic Sea Ice

AbstractOn top of a declining trend driven by global warming, the Arctic sea ice extent (SIE) exhibits considerable interannual variations. In this study, we analyze the interannual anomalies of September SIE in relation to the surface radiation anomalies. We find that the accumulation of radiation energy in the early months (June, July, and August) very well explains the September SIE variability (R2 = 0.81). In Particular, strong correlations are found between September SIE and June radiation anomalies, which in the shortwave is due to cloud and surface albedo changes and in the longwave due to atmospheric warming. The results show that monitoring the radiation anomalies affords a potential means to improve the prediction of the late summer sea ice.

Essential Ingredients to the Dynamics of Westerly Wind Bursts

AbstractWesterly wind bursts (WWBs) are brief, anomalously westerly winds in the tropical Pacific that play a role in the dynamics of ENSO through their forcing of ocean Kelvin waves. They have been associated with atmospheric phenomena such as tropical cyclones, the MJO, and convectively coupled Rossby waves, yet their basic mechanism is not yet well understood. We study WWBs using an aquaplanet general circulation model, and find that eastward-propagating convective heating plays a key role in the generation of model WWBs, consistent with previous studies. Furthermore, wind-induced surface heat exchange (WISHE) acts on a short time scale of about two days to dramatically amplify the model WWB winds near the peak of the event. On the other hand, it is found that radiation feedbacks (i.e., changes in the net radiative anomalies accompanying westerly wind bursts) are not essential for the development of WWBs, and act as a weak negative feedback on WWBs and their associated convection. Similarly, sensible surface heat flux anomalies are not found to have an effect on the development of model WWBs.

Decreased Global 137Cs Fallout Background on an Inspected Territory as an Evidence for Searching for a Radiation Anomaly of a Clandestine Underground Nuclear Explosion or of an Artifact

It was found previously that the density of the soil contamination with 137Cs in some shafts on the Semipalatinsk Test Site appreciably decreased relative to the 137Cs global fallout background. The occurrence of this effect was checked in 1997–1999 around ten shafts prepared for nuclear tests and three shafts after previous nuclear tests. The γ-ray spectra were taken using Ge(Li) and NaI(T1) detectors, and soil samples were taken. The measurements showed that the surface activity of 137Cs did decrease in the radius of approximately 100 m around the surveyed shafts. This is caused by the works performed when making the testing shaft, with movement of the soil cover on the site. This effect can serve as an additional evidence for searching for an undeclared nuclear explosion in on-site inspections.

Flash Drought as Captured by Reanalysis Data: Disentangling the Contributions of Precipitation Deficit and Excess Evapotranspiration

Abstract Flash droughts—uncharacteristically rapid dryings of the land system—are naturally associated with extreme precipitation deficits. Such precipitation deficits, however, do not tell the whole story, for land surface drying can be exacerbated by anomalously high evapotranspiration (ET) rates driven by anomalously high temperatures (e.g., during heat waves), anomalously high incoming radiation (e.g., from reduced cloudiness), and other meteorological anomalies. In this study, the relative contributions of precipitation and ET anomalies to flash drought generation in the Northern Hemisphere are quantified through the analysis of diagnostic fields contained within the MERRA-2 reanalysis product. Unique to the approach is the explicit treatment of soil moisture impacts on ET through relationships diagnosed from the reanalysis data; under this treatment, an ET anomaly that is negative relative to the local long-term climatological mean is still considered positive in terms of its contribution to a flash drought if it is high for the concurrent value of soil moisture. Maps produced in the analysis show the fraction of flash drought production stemming specifically from ET anomalies and illustrate how ET anomalies for some droughts are related to temperature and radiation anomalies. While ET is found to have an important impact on flash drought production in the central United States and in parts of Russia known from past studies to be prone to heat wave–related drought, and while this impact does appear stronger during the onset (first several days) of flash droughts, overall the contribution of ET to these droughts is small relative to the contribution of precipitation deficit.

Atmospheric Dynamics Footprint on the January 2016 Ice Sheet Melting in West Antarctica

AbstractIn January of 2016, the Ross Sea sector of the West Antarctica ice sheet experienced a 3‐week‐long melting episode. Here we quantify the association of the large‐extent and long‐lasting melting event with the enhancement of the downward longwave (LW) radiative fluxes at surface due to water vapor, cloud, and atmospheric dynamic feedbacks using the ERA‐Interim data set. The abnormally long‐lasting temporal surges of atmospheric moisture, warm air, and low‐level clouds increase the downward LW radiative energy flux at the surface during the massive ice‐melting period. The concurrent timing and spatial overlap between poleward wind anomalies and positive downward LW radiative surface energy flux anomalies over West Antarctica due to warmer air temperature and increases in atmospheric water vapor and cloud coverage provide direct evidence that warm and moist air advection from lower latitudes to West Antarctica causes the rapid long‐lasting warming and vast ice mass loss in January of 2016.

Synoptic-scale atmospheric circulation anomalies associated with summertime daily precipitation extremes in the middle–lower reaches of the Yangtze River Basin

The mechanisms of short-lived precipitation extremes in boreal summer over the middle–lower reaches of the Yangtze River Basin (MLYRB) during 1961–2014 are explored using gridded observational and reanalysis datasets. Daily precipitation extremes are defined by the 75th and 95th percentiles and identified for selected regions in the MLYRB. Moisture budget analysis is utilized to quantify the major factors responsible for the variability of extreme precipitation events. Then the atmospheric variables are composited according to these extreme events, to illustrate the temporal evolution of the corresponding synoptic-scale structures. The results show that moisture flux convergence plays a dominant role in the variations of extreme rainfall for both percentile events, and the contribution of evaporation is not evident. Moreover, the dynamic component associated with changes in atmospheric circulation makes a larger contribution than the nonlinear component, followed by the thermodynamic component, owing to changes in specific humidity. The moisture transport pathways increase with increasing magnitude of extreme rainfall intensity. Circulation field anomalies move into the MLYRB during the onset of precipitation extremes for both percentile cases, with stronger anomalies occurring for the 95th percentile cases. Furthermore, the water vapor fluxes transported from the Northwest Pacific are pronounced during the 95th percentile events. A cross-section of specific humidity and vertical gradient of equivalent potential temperature further indicates that dynamic properties play a crucial role in the development of extreme precipitation events linked with quasi-stationary frontal activities across the MLYRB during the past few decades. Composites of Eady growth rate and outgoing longwave radiation anomalies reveal that extratropical cyclones passing through the MLYRB produce a large amount of extreme rainfall by synoptic disturbance.