Joint Planning of Transmission and Distribution Network Considering Wind-solar Complementarity

The temporal and spatial distribution characteristics of wind power and photovoltaic output are complementary to a certain extent, which can stabilize the volatility of single new energy power generation to a certain extent and improve the ability of the grid to absorb new energy. This paper aims to study the joint planning method of power transmission and distribution network considering the complementary characteristics of wind-solar time and space. First, a wind-solar joint distribution model based on the time-varying Copula theory is established, and a wind-solar output simulation method considering the complementary characteristics of time and space is proposed. Then, taking the system investment and new energy consumption capacity as the optimization goals, and taking the system power balance, line transmission capacity, conventional generator set output and climbing capacity as constraints, the joint planning model of transmission and distribution network is established. At last, the analysis of calculation examples proves that the joint planning model of transmission and distribution network considering the complementary characteristics of wind-solar time and space can significantly improve the capacity of the grid to absorb new energy.

Study of the dependence of long-term stratospheric ozone trends on local solar time

Reliable ozone trends after 2000 are essential to detect early ozone recovery. However, the long-term ground-based and satellite ozone profile trends reported in the literature show a high variability. There are multiple reasons for variability in the reported long-term trends such as the measurement timing and the dataset quality. The Payerne Switzerland microwave radiometer (MWR) ozone trends are significantly positive at 2 % to 3 % per decade in the upper stratosphere (5–1 hPa, 35–48 km), with a high variation with altitude. This is in accordance with the Northern Hemisphere (NH) trends reported by other ground-based instruments in the SPARC LOTUS project. In order to determine what part of the variability between different datasets comes from measurement timing, Payerne MWR and SOCOL v3.0 chemistry–climate model (CCM) trends were estimated for each hour of the day with a multiple linear regression model. Trends were quantified as a function of local solar time (LST). In the middle and upper stratosphere, differences as a function of LST are reported for both the MWR and simulated trends for the post-2000 period. However, these differences are not significant at the 95 % confidence level. In the lower mesosphere (1–0.1 hPa, 48–65 km), the 2010–2018 day- and nighttime trends have been considered. Here again, the variation in the trend with LST is not significant at the 95 % confidence level. Based on these results we conclude that significant trend differences between instruments cannot be attributed to a systematic temporal sampling effect. The dataset quality is of primary importance in a reliable trend derivation, and multi-instrument comparison analyses can be used to assess the long-term stability of data records by estimating the drift and bias of instruments. The Payerne MWR dataset has been homogenized to ensure a stable measurement contribution to the ozone profiles and to take into account the effects of three major instrument upgrades. At each instrument upgrade, a correction offset has been calculated using parallel measurements or simultaneous measurements by an independent instrument. At pressure levels smaller than 0.59 hPa (above ∼50 km), the homogenization corrections to be applied to the Payerne MWR ozone profiles are dependent on LST. Due to the lack of reference measurements with a comparable measurement contribution at a high time resolution, a comprehensive homogenization of the sub-daily ozone profiles was possible only for pressure levels larger than 0.59 hPa. The ozone profile dataset from the Payerne MWR, Switzerland, was compared with profiles from the GROMOS MWR in Bern, Switzerland, satellite instruments (MLS, MIPAS, HALOE, SCHIAMACHY, GOMOS), and profiles simulated by the SOCOL v3.0 CCM. The long-term stability and mean biases of the time series were estimated as a function of the measurement time (day- and nighttime). The homogenized Payerne MWR ozone dataset agrees within ±5 % with the MLS dataset over the 30 to 65 km altitude range and within ±10 % of the HARMonized dataset of OZone profiles (HARMOZ, limb and occultation measurements from ENVISAT) over the 30 to 65 km altitude range. In the upper stratosphere, there is a large nighttime difference between Payerne MWR and other datasets, which is likely a result of the mesospheric signal aliasing with lower levels in the stratosphere due to a lower vertical resolution at that altitude. Hence, the induced bias at 55 km is considered an instrumental artifact and is not further analyzed.

Dynamics of the extremely elongated cloud on Mars Arsia Mons volcano

<p>Starting in September 2018, a daily repeating extremely elongated cloud was observed extending from the Mars Arsia Mons volcano. We study this Arsia Mons Elongated Cloud (AMEC) using images from VMC, HRSC, and OMEGA on board Mars Express, IUVS on MAVEN, and MARCI on MRO. We study the daily cycle of this cloud, showing how the morphology and other parameters of the cloud evolved with local time. The cloud expands every morning from the western slope of the volcano, at a westward velocity of around 150m/s, and an altitude of around 30-40km over the local surface. Starting around 2.5 hours after sunrise (8.2 Local True Solar Time, LTST), the formation of the cloud resumes, and the existing cloud keeps moving westward, so it detaches from the volcano, until it evaporates in the following hours. At this time, the cloud has expanded to a length of around 1500km. Short time later, a new local cloud appears on the western slope of the volcano, starting around 9.5 LTST, and grows during the morning.</p><p>This daily cycle repeated regularly for at least 90 sols in 2018, around Southern Solstice (Ls 240-300) in Martian Year (MY) 34. According with these and previous  MEx/VMC observations, this elongated cloud is a seasonal phenomenon occurring around Southern Solstice every Martian Year. We study the interannual variability of this cloud, the influence of the Global Dust Storms in 2018 on the cloud’s properties (Sánchez-Lavega et al., Geophys. Res. Lett. 46, 2019), and its validity as a proxy for the global state of the Martian atmosphere (Sánchez-Lavega et al., J. Geophys. Res., 123, 3020, 2018). We discuss the physical mechanisms behind the formation of this peculiar cloud in Mars.</p>

Study of the dependence of stratospheric ozone long-term trends on local solar time

Multi-instrument comparison analyses are essential to assess the long-term stability of data records by estimating the drift and bias of instruments. The ozone profile dataset from the SOMORA microwave radiometer (MWR) in Payerne, Switzerland, was compared with profiles from the GROMOS MWR in Bern, Switzerland, satellite instruments (MLS, MIPAS, HALOE, SCHIAMACHY, GOMOS), and profiles simulated by the SOCOL v3.0 chemistry-climate model (CCM). The Payerne MWR dataset has been homogenized to ensure a stable measurement contribution to the ozone profiles and to take into account the effects of three major instrument upgrades. At pressure levels smaller than 0.59 hPa (above ~ 50 km), the homogenization corrections to be applied to the Payerne MWR ozone profiles are dependent on local solar time (LST). Due to the lack of reference measurements with a comparable measurement contribution at a high time resolution, a comprehensive homogenization of the sub-daily ozone profiles was possible only for pressure levels larger than 0.59 hPa. The long-term stability and mean biases of the time series were estimated as a function of the measurement time (day- and nighttime). The homogenized Payerne MWR ozone dataset agrees within ± 5 % with the MLS dataset over the 30 to 65 km altitude range and within ± 10 % of HARMOZ datasets over the 30 to 65 km altitude range. In the upper stratosphere, there is a large nighttime difference between Payerne MWR and other datasets, which is likely a result of the mesospheric signal aliasing with lower levels in the stratosphere due to a lower vertical resolution at that altitude. Hence, the induced bias at 55 km is considered an instrumental artefact and is not further analyzed and discussed. In the upper stratosphere (5–1 hPa, 35–48 km), the Payerne MWR trends are significantly positive at 2 to 3 %/decade. This is in accordance with the northern hemisphere (NH) trends reported by other ground-based instruments in the SPARC LOTUS project. The reason for variability in the reported long-term ground-based and satellite ozone profile trends has multiple possibilities. To determine what part of the variability comes from measurement timing, MWR trends were estimated for each hour of the day with a multiple linear regression model to quantify trends as a function of LST. In the mid- and upper stratosphere, differences as a function of LST are reported for both the MWR and simulated trends for the 2000–2016 period. However, these differences are not significant at the 95 % confidence level. In the lower mesosphere (1–0.1 hPa, 48–65 km), the 2010–2018 day- and nighttime trends have been considered. Here again, the variation of the trend with LST is not significant at the 95 % confidence level. Based on these results we conclude that trend differences between instruments cannot to be attributed to a systematic temporal sampling.

Self-orienting armillary dial of the Professor Radovan Danic

Prof. Radovan Danic, PhD (1893-1979), an honorary lifetime President of the Astronomical Society Rudjer Boskovic in Belgrade, owned a brass universal equinoctial ring sundial (98 mm in diameter), preserved by his descendants, who continued his work on popularizing astronomy through the activities of the society. The sundial (ring dial) was measured, tested and compared to similar portable sundials (pocket sundials) exhibited in various European museums. In the classification scheme, along with the Parmenion?s and astronomical rings, it belongs to a group of pocket armillary sundials that do not require a compass. More precisely, it is a self-orienting armillary sundial whose rings are located under the circles of the celestial sphere of the same name at the moment of measurement. Therefore, when the apparent solar time is known, it turns into a solar compass. A corresponding sundial on the horizon to the self-orienting armillary sundial is the analemmatic sundial. The construction of a self-orienting armillary sundial was first described in the late 16th century by the English mathematician William Oughtred (1574-1660). In collaboration with the gnomonists from England and Austria, we determined where and when Professor Danic?s sundial was constructed: Vienna, second quarter of the 18th century. Originally, the sundial was adjusted for the latitude of Belgrade or Zemun (nowadays, a Belgrade municipality), which were under the Austrian rule for a long time during the 18th century. It is a beautiful, well-crafted, well-preserved, expensive sundial and astronomical instrument that should be kept in a museum, in the first place in the Museum of Astronomy of the Astronomical Observatory in Belgrade.

ASTROLABE; INSTRUMEN ASTRONOMI KLASIK DAN KONTRIBUSINYA DALAM HISAB RUKYAT

AbstrakKontribusi Astrolabe sebagai instrumen astronomi klasik tidak boleh dipandang sebelah mata. Peran dan kontribusinya cukup signifikan dalam perkembangan astronomi. Astrolabe secara umum berfungsi untuk menentukan waktu surya (solar time) dengan memanfaatkan fenomena alam, yaitu Matahari pada siang hari dan pengamatan bintang pada malam hari. Kehadiran Astrolabe dengan fungsinya tersebut sangat membantu aktivitas manusia sehari-hari dalam beberapa lini. Astrolabe mengalami modifikasi di tangan umat Islam, karena fungsi instrumen klasik ini selaras dengan syariat Islam, khususnya dalam penentuan awal waktu salat. Masuknya waktu salat dalam hukum Islam didasarkan kepada fenomena alam, seperti tergelincirnya Matahari (zawāl) sebagai tanda masuknya waktu salat zuhur. Kata Kunci: Astrolabe, instrumen astronomi klasik dan hisab rukyat.

Solar-cycle, seasonal, and asymmetric dependencies of thermospheric mass density disturbances due to magnetospheric forcing

Short-term upper atmosphere variations due to magnetospheric forcing are very complex, and neither well understood nor capably modelled due to limited observations. In this paper, mass density variations from 2003–2013 of GRACE observations are isolated through the parameterization of annual, Local-Solar-Time (LST), and solar-cycle fluctuations using a Principal Component Analysis (PCA) technique and investigated in terms of magnetospheric drivers. The magnitude of high-frequency (