A method of estimating longwave radiation Over the Indian seas based on surface synoptic observations

An attempt has been made to estimate longwave radiative flux from sea surface using semi empirical models with the help of routinely observed meteorological parameters during the monsoon season. The estimated values are then compared with observed values to find out an appropriate method to compute a longwave flux. The study shows that clouds play an important role in determining the longwave flux. It IS found that lack of detailed knowledge of clouds obtained from ground based observations is responsible for the errors in the estimation of longwave flux. The errors are reduced using a regression method based on Monsoon-77 data set. The method was then tested with Monex-79 data set which served as independent data set. The method thus developed considerably reduces the errors associated with the estimation of long wave flux.

The Atacama Cosmology Telescope: A Search for Planet 9

We use Atacama Cosmology Telescope (ACT) observations at 98 GHz (2015–2019), 150 GHz (2013–2019), and 229 GHz (2017–2019) to perform a blind shift-and-stack search for Planet 9. The search explores distances from 300 au to 2000 au and velocities up to 6.′3 per year, depending on the distance (r). For a 5 Earth-mass Planet 9 the detection limit varies from 325 au to 625 au, depending on the sky location. For a 10 Earth-mass planet the corresponding range is 425 au to 775 au. The predicted aphelion and most likely location of the planet corresponds to the shallower end of these ranges. The search covers the whole 18,000 square degrees of the ACT survey. No significant detections are found, which is used to place limits on the millimeter-wave flux density of Planet 9 over much of its orbit. Overall we eliminate roughly 17% and 9% of the parameter space for a 5 and 10 Earth-mass Planet 9, respectively. These bounds approach those of a recent INPOP19a ephemeris-based analysis, but do not exceed it. We also provide a list of the 10 strongest candidates from the search for possible follow-up. More generally, we exclude (at 95% confidence) the presence of an unknown solar system object within our survey area brighter than 4–12 mJy (depending on position) at 150 GHz with current distance 300 au < r < 600 au and heliocentric angular velocity 1 .′ 5 yr − 1 < v · 500 au r < 2 .″ 3 yr − 1 , corresponding to low-to-moderate eccentricities. These limits worsen gradually beyond 600 au, reaching 5–15 mJy by 1500 au.

Acoustic Wave Properties in Footpoints of Coronal Loops in 3D MHD Simulations

Acoustic waves excited in the photosphere and below might play an integral part in the heating of the solar chromosphere and corona. However, it is yet not fully clear how much of the initially acoustic wave flux reaches the corona and in what form. We investigate the wave propagation, damping, transmission, and conversion in the lower layers of the solar atmosphere using 3D numerical MHD simulations. A model of a gravitationally stratified expanding straight coronal loop, stretching from photosphere to photosphere, is perturbed at one footpoint by an acoustic driver with a period of 370 s. For this period, acoustic cutoff regions are present below the transition region (TR). About 2% of the initial energy from the driver reaches the corona. The shape of the cutoff regions and the height of the TR show a highly dynamic behavior. Taking only the driven waves into account, the waves have a propagating nature below and above the cutoff region, but are standing and evanescent within the cutoff region. Studying the driven waves together with the background motions in the model reveals standing waves between the cutoff region and the TR. These standing waves cause an oscillation of the TR height. In addition, fast or leaky sausage body-like waves might have been excited close to the base of the loop. These waves then possibly convert to fast or leaky sausage surface-like waves at the top of the main cutoff region, followed by a conversion to slow sausage body-like waves around the TR.

The Efficiency of Upward Wave Propagation Near the Tropopause: importance of the form of the refractive index

The connection between the polar stratospheric vortex and the vertical component of the Eliassen-Palm flux in the lower stratosphere and upper troposphere is examined in model level data from the ERA-5 reanalysis. The particular focus of this work is on the conditions that lead to upward wave propagation between the tropopause and the bottom of the vortex near 100 hPa. The ability of four different versions of the index of refraction to capture this wave propagation are evaluated. The original Charney and Drazin index of refraction includes terms ignored by Matsuno that are shown to be critical for understanding upward wave propagation just above the tropopause in both the climatology and during extreme heat flux events. By adding these terms to the Matsuno index of refraction, it is possible to construct a useful tool that describes wave flux immediately above the tropopause and at the same time also describes the role of meridional variations within the stratosphere. It is shown that a stronger tropopause inversion layer tends to restrict upward wave propagation. It is also shown that while only 38% of extreme wave-1 Eliassen-Palm flux vertical component (Fz) at 100hPa events are preceded by extreme Fz at 300hPa, there are almost no extreme events at 100hPa in which the anomaly at 300hPa is of opposite sign or very weak. Overall, wave propagation near the tropopause is sensitive to vertical gradients in buoyancy frequency, and these vertical gradients may not be accurately captured in models or reanalysis products especially with lower vertical resolutions.

Characteristics of Aerosol and Effect of Aerosol-Radiation-Feedback in Handan, an Industrialized and Polluted City in China in Haze Episodes

In order to investigate the chemical characteristics of aerosol pollution including PM1 and PM2.5 in Handan, the offline sampling campaign was conducted and the concentrations of total water-soluble inorganic ions (TWSI), carbonaceous components (OC and EC) were analyzed. The average concentrations were 88.5 μg/m3 for PM1 and 122 μg/m3 for PM2.5, and the corresponding ratios of PM1 versus PM2.5 on non-pollution, mild-moderate pollution and heavy pollution were 0.67, 0.70 and 0.77, respectively. TWSI and OC accounted for 43.2% and 15.4% in PM1, 41.8% and 16.0% in PM2.5. Secondary components in PM2.5 and PM1 increased with heavy pollution, SNA (SO42−, NO3− and NH4+) was enriched in PM1 but SOC (Secondary Organic Carbon) was more enriched in PM1–2.5. Furthermore, for evaluating the effect of aerosol feedback the WRF-Chem model was applied to identify the aerosol-radiation interaction of aerosol feedback influence on the PM2.5 concentration and various meteorological factors in Handan. The results indicated that the aerosol radiative effects will result in an average 32.62%(36.18 W/m2) decrease in downward short wave flux at ground surface (SWDOWN), an average 17.52% (39.15 m) and 0.16% (0.44 K) decrease in planetary boundary layer height(PBLH) and surface temperature (T2). The wind speed at 10 m (WS) and relative humidity (RH) will be increased by about 4.16%(0.11 m/s) and 1.89% (0.78%), respectively.

Longitudinal peculiarities of planetary waves-zonal flow interaction and its role in stratosphere-troposphere dynamical coupling

The three-dimensional (3D) planetary wave analysis provides more regionalized information on stratospheric-tropospheric dynamic interactions. The upward wave flux from the troposphere to the stratosphere is maximized above north-eastern Eurasia, while the downward flux is mainly over the North America and North Atlantic (NANA) region, which is much stronger in mid and late winter. This distribution is determined by the wave-wave interaction between the different wavenumbers of planetary waves, especially between wavenumber 1 and wavenumber 2. The upward wave flux anomalies in early winter are negatively correlated with the strength of the stratospheric polar vortex (SPV). In the mid and late winter months, the strength of the SPV is positively correlated with the first mode of 3D wave flux and has a leading relationship of approximately one month. The stronger SPV corresponds to a stronger upward wave flux above northern Eurasia and stronger downward flux over the NANA region. The interannual variation in wave flux in early winter is closely associated with the Scandinavian wave train pattern. In contrast, the wave flux variation is related to the circulation anomaly corresponding to Arctic Oscillation in mid and late winter, which causes climate anomalies across the Northern Hemisphere, especially coherent temperature changes in northern Europe, eastern United States and northeastern China.

Optimizing COSMO_REA6 reanalysis radiation flux for a high resolution coastal ocean model

&lt;p&gt;When modelling coastal areas in high spatial resolution, it is also essential to obtain atmospheric forcing with suitably fine grid. The complex coastline and coastal orography exert strong influence on atmospheric fields, wind in particular, and the east Adriatic coast with numerous islands and coastal mountain ridges is a fine example. We decided to use a high resolution COSMO atmospheric reanalysis for our long term ROMS_AGRIF hindcasts, but in our initial experiments we found out that the atmospheric model significantly underestimates the short wave flux over the Mediterranean Sea, probably due to overestimation of high clouds formation and erroneous sea surface temperature used as a boundary condition. We explore different atmospheric models and different combinations of fluxes - direct, diffuse and clear sky solar radiation and combinations of fluxes from different atmospheric models (eg. ERA5). We compare them with solar irradiance observations at a coastal meteorological station and run year-long simulations to compare model sea surface temperature (SST) with satellite observations obtained from Coprenicus Marine Environment Monitoring Service.&lt;/p&gt;

Bay of Bengal‐East Asia‐Pacific Teleconnection in Boreal Summer

&lt;p&gt;A new teleconnection pattern (the BEAP) across the Bay of Bengal&amp;#8208;East Asia&amp;#8208;Pacific region in boreal summer is revealed in this study using mainly ERA&amp;#8208;Interim reanalysis data from the European Centre for Medium&amp;#8208;Range Weather Forecasts. The BEAP index (BEAPI) is defined as the signed sum of standardized apparent moisture sinks at five centers along the pathway. Correlation analysis of the apparent heat sources and apparent moisture sinks has verified the existence of the BEAP teleconnection. Variations in BEAP can affect precipitation anomalies resulting from the anomalous moisture transport and the antiphase surface temperature variation. Wave flux analysis has verified the Rossby wave propagation route that originates around the central Bay of Bengal and extends across North China to the West Pacific. La Ni&amp;#241;a&amp;#8208;type sea surface temperature anomalies (SSTAs) appearing simultaneously in the same season can excite a positive BEAP pattern by enhancing convection over the Bay of Bengal, while El Ni&amp;#241;o&amp;#8208;type SSTAs have the opposite effect. Significant correlation between the BEAPI and the SSTAs can last from early summer to early winter. Numerical experiments confirm the BEAP teleconnection pattern and the associated physical processes.&lt;/p&gt;

The role of wave–wave interactions in sudden stratospheric warming formation

The effects of wave–wave interactions on sudden stratospheric warming formation are investigated using an idealized atmospheric general circulation model, in which tropospheric heating perturbations of zonal wave numbers 1 and 2 are used to produce planetary-scale wave activity. Zonal wave–wave interactions are removed at different vertical extents of the atmosphere in order to examine the sensitivity of stratospheric circulation to local changes in wave–wave interactions. We show that the effects of wave–wave interactions on sudden warming formation, including sudden warming frequencies, are strongly dependent on the wave number of the tropospheric forcing and the vertical levels where wave–wave interactions are removed. Significant changes in sudden warming frequencies are evident when wave–wave interactions are removed even when the lower-stratospheric wave forcing does not change, highlighting the fact that the upper stratosphere is not a passive recipient of wave forcing from below. We find that while wave–wave interactions are required in the troposphere and lower stratosphere to produce displacements when wave number 2 heating is used, both splits and displacements can be produced without wave–wave interactions in the troposphere and lower stratosphere when the model is forced by wave number 1 heating. We suggest that the relative strengths of wave number 1 and 2 vertical wave flux entering the stratosphere largely determine the split and displacement ratios when wave number 2 forcing is used but not wave number 1.