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.

Statistical postprocessing of heavy precipitation

<p>Heavy precipitation rates of more than 15 mm per hour are captured only about once a year at each rain gauge within Germany. More extreme events are even less frequent. Point by point verifications show that forecasts of heavy precipitation of the ensemble system COSMO-D2-EPS of DWD can be improved by statistical postprocessing. This is done in a MOS approach using long time series of synoptic observations and numerical forecasts that are required in or­der to gather a significant number of heavy precipitation events for reliable statistical model­ling.</p><p>Highest precipitation rates of convective events usually realise more likely in the surrounding of rain gauges rather than exactly above their small funnels. Statistical forecasts modelling these point observations usually underestimate maximal rain rates and result in low probabili­ties for the occurrence of heavy precipitation at a given location.</p><p>Point processes of stochastic geometry can be used to model area probabilities that provide the probability that precipitation occurs anywhere (at least at one point) within that area. Verifications with gauge adjusted radar data reveal that point probabilities are representative for very small areas, but area probabilities are significantly larger already for areas of 20*20 km<sup>2</sup>.</p><p>The use of radar data as area observation system allows to statistically generate calibrated precipitation forecasts for arbitrary areas. However, the question remains, which size of area is most relevant for the public and most suitable for weather warnings.</p>

Application of a new scale-aware three-dimensional subgrid mixing parameterization on the simulations of tropical cyclone

<p>A new scale-adaptive three-dimensional (3D) turbulent kinetic energy (TKE) subgrid mixing scheme is developed using the Advanced Research version of the Weather Research and Forecasting Model (WRF-ARW) to address the gray-zone problem in the parameterization of subgrid turbulent mixing. This scheme is based on the full 3D TKE prognostic equation and combines the horizontal and vertical subgrid turbulent mixing into a single energetically consistent framework.</p><p>A series of real tropical cyclone(TC) simulations with varying horizontal resolutions from 9km to 1km are carried out to compare the performance of the 3D mixing scheme and the conventional 1D planetary boundary layer (PBL) schemes to the observations, including conventional ones such as radiosonde and surface synoptic observations, as well as intensive ones obtained during the landfall of TC, such as mobile boundary layer wind profiler and Dual-pol Doppler Radar. This study aims to determine if the new scheme performs appropriate on TC simulation, and to evaluate the sensitivity of TC simulation to boundary layer schemes.</p>

Synoptic solar observations of the Solar Flare Telescope focusing on space weather

The solar group at the National Astronomical Observatory of Japan is conducting synoptic solar observation with the Solar Flare Telescope. While it is a part of a long-term solar monitoring, contributing to the study of solar dynamo governing solar activity cycles, it is also an attempt at contributing to space weather research. The observations include imaging with filters for Hα, Ca K, G-band, and continuum, and spectropolarimetry at the wavelength bands including the He I 1083.0 nm/Si I 1082.7 nm and the Fe I 1564.8 nm lines. Data for the brightness, Doppler signal, and magnetic field information of the photosphere and the chromosphere are obtained. In addition to monitoring dynamic phenomena like flares and filament eruptions, we can track the evolution of the magnetic fields that drive them on the basis of these data. Furthermore, the magnetic field in solar filaments, which develops into a part of the interplanetary magnetic cloud after their eruption and occasionally hits the Earth, can be inferred in its pre-eruption configuration. Such observations beyond mere classical monitoring of the Sun will hereafter become crucially important from the viewpoint of the prediction of space weather phenomena. The current synoptic observations with the Solar Flare Telescope is considered to be a pioneering one for future synoptic observations of the Sun with advanced instruments.

Solar surveillance with CLIMSO: instrumentation, database and on-going developments

CLIMSO is a suite of solar telescopes installed at Pic du Midi observatory in the southwest of France. It consists of two refractors that image the full solar disk in Hα and CaII K, and two coronagraphs that capture the prominences and ejections of chromospheric matter in Hα and HeI. Synoptic observations are carried out since 2007 and they follow those of previous instruments. CLIMSO, together with its predecessors, offer a temporal coverage of several solar cycles. With a direct access to its images, CLIMSO contributes to real time monitoring of the Sun. For that matter, the national research council for astrophysics (CNRS/INSU) has labelled CLIMSO as a national observation service for “surveillance of the Sun and the terrestrial space environment”. Products, under the form of images, movies or data files, are available via the CLIMSO DataBase. In this paper, we present the current instrumental configuration; we detail the available products and show how to access them; we mention some possible applications for solar and space weather; and finally, we evoke developments underway, both numerical to valorise our data, and instrumental to offer more and better capabilities.

Eddy Detection in HF Radar-Derived Surface Currents in the Gulf of Naples

Submesoscale eddies play an important role in the energy transfer from the mesoscale down to the dissipative range, as well as in tracer transport. They carry inorganic matter, nutrients and biomass; in addition, they may act as pollutant conveyors. However, synoptic observations of these features need high resolution sampling, in both time and space, making their identification challenging. Therefore, HF coastal radar were and are successfully used to accurately identify, track and describe them. In this paper we tested two already existing algorithms for the automated detection of submesoscale eddies. We applied these algorithms to HF radar velocity fields measured by a network of three radar systems operating in the Gulf of Naples. Both methods showed shortcomings, due to the high non-geostrophy of the observed currents. For this reason we developed a third, novel algorithm that proved to be able to detect highly asymmetrical eddies, often not properly identified by the previous ones. We used the results of the application of this algorithm to estimate the eddy boundary profiles and the eddy spatial distribution.

Solar observations at the Coimbra Astronomical Observatory

In 2020, the Geophysical and Astronomical Observatory of the University of Coimbra will celebrate the 95th anniversary of its first spectroheliographic observation. Keeping a daily service of solar observations since then, making almost a century, led to one of the largest continuous solar data collections in the world. This long–term solar database is essential for studies where solar activity is involved. This work reviews the development of synoptic observations made at the Observatory of Coimbra since 1925 and presents a summary of some of the principal stages of the Observatory’s history since its founding in 1772. We refer the main technical improvements and present some perspectives for the near future. One of the most significant upgrades was the installation of a CCD camera in 2007. The transition from photographic emulsion to digital recording methods allowed the development of image analysis algorithms to process solar images and improved data sharing with other institutions. This upgrade enabled also to carry–out modern climate and space weather studies. This valuable advancement makes it possible to create a new catalogue of solar observations to be published in the future.

SYNOPTIC OBSERVATIONS OF CALVING EVENTS IN ANTARCTICA USING SPACEBORNE IMAGES

<p><strong>Abstract.</strong> Iceberg calving is the detachment of ice from ice shelves or glaciers. Although calving is a natural phenomenon, an abnormal rate of calving can be a threat to ice shelves. Some of the events were so large, that an iceberg of approximately 150<span class="thinspace"></span>&amp;times;<span class="thinspace"></span>50<span class="thinspace"></span>km area was calved in a single event. The most recent reported iceberg calving event was Larsen C and it took place in July 2017. In addition to the large and widely reported calving events, there are several small calving events, which are also of great significance and contribute to the overall mass loss from Antarctica. This study focuses on small calving events in Antarctica along various coasts. Three calving events are studied here, all of them have occurred in the past. This study was performed using Google Earth and Landsat satellite imageries. The first event is identified to have occurred at the Knox coast in 2016. Even after the icebergs were calved, they remained intact with the ice shelf due to ice fronts. The second event took place at the Queen Mary Coast in the year 2014. This event was studied from 2009 to 2016 using Landsat satellite images and many rifts were observed. The third event took place at the Princess Astrid Coast in the year 2016. This event was monitored from 2014 and three icebergs were calved between the years 2014 to 2016. This study emphasizes the exploitation of optical satellite data for studying calving events in Antarctica. Various crevasses and rifts are observed on Landsat imageries, which can be the first sign of a calving process.</p>

Constructing a precipitable water vapor map from regional GNSS network observations without collocated meteorological data for weather forecasting

Surface pressure (Ps) and weighted mean temperature (Tm) are two necessary variables for the accurate retrieval of precipitable water vapor (PWV) from Global Navigation Satellite System (GNSS) zenith total delay (ZTD) estimates. The lack of Ps or Tm information is a concern for those GNSS sites that are not collocated with meteorological sensors. This paper investigates an alternative method of inferring accurate Ps and Tm at the GNSS station using nearby synoptic observations. Ps and Tm obtained at the nearby synoptic sites are interpolated onto the location of the GNSS station by performing both vertical and horizontal adjustments, in which the parameters involved in Ps and Tm calculation are estimated from ERA-Interim reanalysis profiles. In addition, we present a method of constructing high-quality PWV maps through vertical reduction and horizontal interpolation of the retrieved GNSS PWVs. To evaluate the performances of the Ps and Tm retrieval, and the PWV map construction, GNSS data collected from 58 stations of the Hunan GNSS network and synoptic observations from 20 nearby sites in 2015 were processed to extract the PWV so as to subsequently generate the PWV maps. The retrieved Ps and Tm and constructed PWV maps were assessed by the results derived from radiosonde and the ERA-Interim reanalysis. The results show that (1) accuracies of Ps and Tm derived by synoptic interpolation are within the range of 1.7–3.0 hPa and 2.5–3.0 K, respectively, which are much better than the GPT2w model; (2) the constructed PWV maps have good agreements with radiosonde and ERA-Interim reanalysis data with the overall accuracy being better than 3 mm; and (3) PWV maps can well reveal the moisture advection, transportation and convergence during heavy rainfall.