Tropical variability simulated in ICON-A with a spectral cumulus parameterization

We implemented a spectral cumulus parameterization based on a cloud-resolving model (SC scheme) in the icosahedral nonhydrostatic atmospheric model (ICON-A). We compared the resulting simulated climatology and tropical variability with results from the standard version of ICON-A using a variant of the Tiedtke-Nordeng scheme (TK scheme) using observational and reanalysis data. The climatological errors of the SC scheme were similar to those of the TK scheme, but several biases, such as properties of meridional winds and precipitation pattern in the western Pacific, were much improved. For tropical variability, we found that the SC scheme improved the interannual response of the precipitation in the western Pacific and was able to simulate Madden-Julian oscillation (MJO) features much better than the TK scheme. We investigated the reason for the better simulation of the MJO using composite analysis and column process analysis for moisture. Our results suggest that the entrainment parameterization of the SC scheme is necessary to reproduce the MJO; however, spectral representation and improved convective closure are also found to contribute for better MJO simulation. These parameterizations improved moisture supply from low-level clouds and cloud mass flux which were needed to sustain the MJO. © 2019. The Authors

Diagnostic role of the growth of fetal abdominal circumference measurement in the identification of small fetuses for the gestational age in high-risk pregnancies using the intergrowth-21st curves

Lo scopo del lavoro è stato quello di valutare se i feti SGA presentassero un incremento ridotto della circonferenza addominale rispetto ai feti AGA e comprendere se questo potesse avere un ruolo diagnostico nell’identificare i feti a rischio di sviluppare ritardo di crescita; calcolare poi l’accuratezza diagnostica nelle diverse epoche e valutare il contributo diagnostico degli esami ecografici longitudinali eseguiti dopo 24 settimane. Sono state selezionate pazienti viste consecutivamente per la presenza di fattori di rischio per restrizione di crescita e raccolte le misurazioni della CA. Su un totale di 420 donne e 1240 ecografie 151 feti erano SGA. Nella popolazione di gravide ad alto rischio i feti SGA e AGA presentano una velocità di crescita simile e statisticamente non diversa. La velocità di crescita correla debolmente con il basso peso alla nascita, per cui aggiungere il dato velocità di crescita in due esami indipendenti a distanza di 2-4 settimane al semplice z-score della CA nel primo esame non migliora la accuratezza diagnostica. Una piccola quota dei feti presenta un arresto della crescita, che si manifesta mediamente a 35 settimane; tali feti vengono partoriti prima e sono mediamente più piccoli, sia in valore assoluto che relativamente all’epoca gestazionale, con un maggiore tasso di complicazioni neonatali.The aim of the work was to evaluate if the SGA fetuses presented a reduced increase in the abdominal circumference compared to the AGA fetuses and to understand if this could have a diagnostic role in identifying fetuses at risk of developing growth delay on the basis of an increase reduced CA; calculate the diagnostic accuracy in the different periods of pregnancy and evaluate the diagnostic contribution of longitudinal ultrasound examinations in the third trimester of pregnancy. Patients viewed consecutively at the ultrasound clinics were selected for the presence of risk factors for fetal growth restriction and fetal CA measurements were recorded at each examination performed in III trimester. Of a total of 420 women, with 1240 ultrasound scans,151 fetuses were SGA. In the high risk population, the SGA and AGA fetuses have a similar and not statistically different growth rate. The growth rate correlates with the LBW, but weakly, so adding the given growth rate in two independent examinations at 2-4 weeks to the simple CA z-score in the first exam does not improve the diagnostic accuracy. A small proportion of fetuses has a growth arrest, which occurs at 35 weeks; fetuses with growth arrest are born before and are on average smaller, both in absolute and in relation to gestational age and have a greater rate of neonatal complications. The SGA and AGA fetuses have a similar and statistically not different growth rate and the longitudinal controls of fetal growth are not very influential for the diagnosis and management of fetuses at risk of being SGA, except for that modest portion of fetuses that in the last part of pregnancy show a stop of growth. These fetuses are slightly smaller and have a slightly increased risk of complications, that may be secondary to the increased iatrogenic prematurity

STUDI EVALUASI DISTRIBUSI TEGANGAN PADA ISOLATOR RANTAI

Untuk Memenuhi Tingkat Keandalan Yang Memadai Dalam Hubungan Dengan Kebutuhan Energi Listrik Di Siantan-Tayan, Yang Harus Meningkat Dari Waktu Ke Waktu, Dilakukan Penyaluran Daya Listrik Dalam Jumlah Yang Besar Pada Kelistrikan Siantan-Tayan Melalui Saluran Udara Tegangan Tinggi (SUTT) 150 KV. Penelitian Ini Bertujuan Untuk Menghitung Distribusi Tegangan Pada Isolator String Dan Efek Ketidak Seragaman Isolator Pada Jaringan Transmisi 150 KV Siantan-Tayan, Menggunakan Metode Pendekatan Diffrensial, Pengaruh Kapasitansi Masing-Masing Isolator (C), Pengaruh Kapasitansi Antara Sambungan Isolator Dengan Menara Atau Ground (Ce) Dan Pengaruh Kapasitansi Antara Sambungan Isolator Dengan Konduktor Tegangan Tinggi Ch

Il sistema archivistico italiano

L’articolo descrive il sistema archivistico italiano, che prevede specifici istituti di concentrazione e conservazione per la sezione storica degli archivi prodotti dagli uffici dello Stato e affida agli enti produttori, pubblici o privati, la gestione e la conservazione dei loro documenti. Inoltre illustra iniziative di valorizzazione e di conservazione concentrata di particolari tipologie di archivi a rischio di dispersione. Infine ricorda i principali temi di ricerca che si sono sviluppati negli ultimi anni, indicando le criticità non ancora risolte e i progetti tuttora in corso.The author describes the Italian archival system: in Italy the preservation of historical archives are managed by different institutions. The Archivi di Stato and the Archivio Centrale dello Stato are specific institutions charged of the concentration and the preservation of the historical sections of archives created by State offices, but the archives created by public or private corporate bodies are managed and preserved by their own creators during all phases of archive life. She talks about many initiatives to improve and to preserve, also in concentrated way some typologies of archives that are at-risk. Finally she illustrates the main research subjects and recent studies; she indicates the must important programmes developed in the last years and shows unresolved critical aspects and some projects in progress.L’articolo descrive il sistema archivistico italiano, che prevede specifici istituti di concentrazione e conservazione per la sezione storica degli archivi prodotti dagli uffici dello Stato e affida agli enti produttori, pubblici o privati, la gestione e la conservazione dei loro documenti. Inoltre illustra iniziative di valorizzazione e di conservazione concentrata di particolari tipologie di archivi a rischio di dispersione. Infine ricorda i principali temi di ricerca che si sono sviluppati negli ultimi anni, indicando le criticità non ancora risolte e i progetti tuttora in corso

Net effect of the QBO in a Chemistry Climate Model

The quasi-biennial oscillation (QBO) of zonal wind is a prominent mode of variability in the tropical stratosphere. It affects not only the meridional circulation and temperature over a wide latitude range but also the transport and chemistry of trace gases such as ozone. Compared to a QBO less circulation, the long-term climatological means of these quantities are also different. These climatological net effects of the QBO can be studied in general circulation models that extend into the middle atmosphere and have a chemistry and transport component, so-called Chemistry Climate Models (CCMs). In this work we show that the CCM MAECHAM4-CHEM can reproduce the observed QBO variations in temperature and ozone mole fractions when nudged towards observed winds. In particular, it is shown that the QBO signal in transport of nitrogen oxides NOx plays an important role in reproducing the observed ozone QBO, which features a phase reversal slightly below the level of maximum of the ozone mole fraction in the tropics. We then compare two 20-year experiments with the MAECHAM4-CHEM model that differ by including or not including the QBO. The mean wind fields differ between the two model runs, especially during summer and fall seasons in both hemispheres. The differences in the wind field lead to differences in the meridional circulation, by the same mechanism that causes the QBO's secondary meridional circulation, and thereby affect mean temperatures and the mean transport of tracers. In the tropics, the net effect on ozone is mostly due to net differences in upwelling and, higher up, the associated temperature change. We show that a net surplus of up to 15% in NOx in the tropics above 10 hPa in the experiment that includes the QBO does not lead to significantly different volume mixing ratios of ozone. We also note a slight increase in the southern vortex strength as well as earlier vortex formation in northern winter. Polar temperatures differ accordingly. Differences in the strength of the Brewer-Dobson circulation and in further trace gas concentrations are analysed. Our findings underline the importance of a representation of the QBO in CCMs

A large-eddy simulation study on the diurnally evolving nonlinear trapped lee waves over a two-dimensional steep mountain

The diurnally evolving trapped lee wave over a small-scale two-dimensional steep mountain is investigated in large eddy simulations based on a fully compressible and non-hydrostatic model (ICON) with triangular grids of 50-m-edge length. An idealized atmospheric profile derived from a realistic case is designed to account for influences from the stagnant layer near the surface, the stability of the atmospheric boundary layer (ABL) and the upper-level jet. Firstly, simulations were done to bridge from the linear regime to the nonlinear regime by increasing the mountain height, which showed that larger amplitude lee waves with longer wavelength can be produced in the nonlinear regime than in the linear regime. Secondly, the effects of the stagnant layer near the surface and the ABL stability were explored, which showed that the stagnant layer or the stable ABL can play a similar wave-absorbing role in the nonlinear regime as in linear theories or simulations. Thirdly, the role of the upper-level jet was explored, indicating that a stronger (weaker) upper-level jet can help to produce longer (shorter) lee waves. The stable ABL with a stagnant layer can more (less) efficiently absorb the longer (shorter) lee waves due to the stronger (weaker) jet, so that the wave response is more sensitive to the wave-absorption layer when an upper-level jet is present. Finally, the momentum budget was analyzed to explore the interaction between the upper and lower levels of the troposphere, which showed that the momentum flux due to the upward-propagating waves and trapped waves varies with the upper-level jet strength and low-level stagnancy and ABL stability

Wave forcing of the quasi-biennial oscillation in the Max Planck Institute Earth System Model

This study investigates the resolved wave forcing of the quasi-biennial oscillation (QBO) in the Max Planck Institute Earth System Model truncated at T63 with 95 vertical levels. The model, which parameterizes unresolved gravity waves, internally generates a QBO. The resolved waves contribute up to 50% and 30% to the total wave forcing (resolved plus parameterized) of the QBO westerly and easterly jet, respectively, mostly owing to waves with zonal wavenumbers lower than 20 and frequencies lower than 0.5 cpd. At higher frequencies and wavenumbers, the model underestimates the strength of the tropospheric wave sources when compared to Tropical Rainfall Measuring Mission (TRMM) observations and applies strong horizontal diffusion, which explains the shortage of wave momentum at these scales (relative to recent studies based on high-resolution models). The study further relates the vertical structure of equatorial Kelvin waves, which contribute most to the transport and deposition of westerly wave momentum, to their radiative dissipation and compares the role of longwave radiation and horizontal diffusion in the dissipation of the resolved waves in general. The Kelvin waves adjust their vertical wavelength according to their intrinsic phase speed and are efficiently damped by longwave radiation within westerly flow, where the vertical wavelength strongly decreases. Waves with zonal wavenumbers larger than 10, however, are mostly damped by horizontal diffusion. The latitudinal distribution of the resolved wave forcing reflects the latitudinal structure of the waves and is asymmetric with respect to the equator. © 2014 American Meteorological Society

Differences between the QBO in the first and in the second half of the ERA-40 reanalysis

International audienceThe representation of the quasi-biennial oscillation (QBO) is investigated in the ERA-40 reanalysis. In the lower stratosphere, where there is a good number of observations, the representation of the QBO is equally well throughout the record. However, strong differences between the first and the second half of the zonal wind data set are found in the upper stratosphere, with a typical offset of ?10 m/s in the equatorial zonal wind in the earlier part versus the later part of the ERA-40 data set. The strength of the QBO is also affected. Possible explanations are discussed. The identified change of the assimilated wind profiles over time in ERA-40 requires a careful use of equatorial upper stratospheric winds from the reanalysis for validation purposes