Seamless Detection of Cutoff Lows and Preexisting Troughs

We propose a new scheme based on geopotential height fields to detect cutoff lows starting in the preexisting trough stage. The intensity and scale derived from the proposed scheme will allow for a better understanding of the cutoff low life cycle. These cutoff lows often accompany mesoscale disturbances, causing adverse weather-related events, such as intense torrential rainfall and/or tornadoes. The proposed scheme quantifies the geometric features of a depression from its horizontal height profile. The height slope of a line intersecting the depression bottom and the nearest tangential point (optimal slope) locally indicates the intensity and scale of an isolated depression.The strength of the proposed scheme is that, by removing a local background height slope from a geopotential height field, the cutoff low and its preexisting trough are seamlessly detected as an identical depression. The distribution maps for the detected cutoff lows and preexisting troughs are illustrated along with their intensities, sizes, and local background flows estimated from snapshot height fields. We conducted climatological comparisons of cutoff lows to determine the utility of the proposed scheme.

Probabilistic Forecasting of the 500 hPa Geopotential Height over the Northern Hemisphere Using TIGGE Multi-model Ensemble Forecasts

Bayesian model averaging (BMA) and ensemble model output statistics (EMOS) were used to improve the prediction skill of the 500 hPa geopotential height field over the northern hemisphere with lead times of 1–7 days based on ensemble forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF), National Centers for Environmental Prediction (NCEP), and UK Met Office (UKMO) ensemble prediction systems. The performance of BMA and EMOS were compared with each other and with the raw ensembles and climatological forecasts from the perspective of both deterministic and probabilistic forecasting. The results show that the deterministic forecasts of the 500 hPa geopotential height distribution obtained from BMA and EMOS are more similar to the observed distribution than the raw ensembles, especially for the prediction of the western Pacific subtropical high. BMA and EMOS provide a better calibrated and sharper probability density function than the raw ensembles. They are also superior to the raw ensembles and climatological forecasts according to the Brier score and the Brier skill score. Comparisons between BMA and EMOS show that EMOS performs slightly better for lead times of 1–4 days, whereas BMA performs better for longer lead times. In general, BMA and EMOS both improve the prediction skill of the 500 hPa geopotential height field.

METHOD OF COMPARATIVE VARIETY ASSESSMENT OF ORNAMENTAL PLANTS

At the present development stage of the ornamental plants selection, there are almost no clear guidelines on the methodology for carrying out variety assessment. Applying the methods used in vegetable and fruit growing for the variety assessment of ornamental crops is incorrect due to the fact that when assessing varieties in ornamental gardening, the leading role belongs to such quality indicators as: color and shape of a leaf, flower or inflorescence, terry, aroma, number of peduncles etc. In addition, such important indicators for industrial floriculture or landscaping of territories as resistance to lodging, resistance to diseases and pests are taken into account indirectly. A characteristic feature of ornamental gardening, in contrast to vegetable growing and fruit growing, is the presence of a very wide variety of varieties within one species, differing in color, doubleness, height, field of use and other qualities, which is extremely important to take into account when carrying out a variety assessment. An integrated method of comparative variety assessment of ornamental plants, when converting all characteristics into relative values (points), simplifies selection and allows choosing the best varieties and hybrids in terms of decorative characteristics that best meet the requirements of modern production. At the same time, as a result of targeted selection, carried out within the relevant garden groups, a recommended assortment is formed, and it covers all existing typical flower colors, including early, middle and late varieties, in terms of flowering time, allowing to prolong the flowering of this crop. The developed methodology for a comprehensive assessment makes it possible to include in the modern assortment varieties that meet various purposes: for cutting in the open field, for forcing in greenhouse complexes and greenhouses, for landscaping gardens and parks.

Extraction of Mauritia flexuosa in Orthophotos Obtained by UAV

The veredas are more than a phytophysiognomy. They constitute a wetland ecosystem that embraces different species in the Cerrado biome. The buriti (Mauritia flexuosa) is the main arboreal species of these environments, has economic relevance and its shape contributes to the identification of the veredas. This study aims to explore the potential of remote sensing for extraction of features using the techniques of segmentation and supervised classification. The area of study was located in Uberlândia, Minas Gerais/Brazil. A database containing field information and orthophoto obtained by UAV, with spatial resolution of 3.5 cm was necessary to use the multiresolution segmentation algorithm of eCognition. The results showed the efficiency of the method, with detection of 75.56% of the M. flexuosa species in the scene. When considering the band of altimetry, the result was 21.61% higher, with a global accuracy of 97%. The RMSE after field validation was 1.14 m. With the collected data and the results, it was possible to extract relevant ontological information, such as the average treetop diameter, shape, leaf length, height, field distribution pattern and spectral response of the target. These parameters can support and contribute to the monitoring and conservation of the species and the vereda environment.

Analysis of the Dominant Spatial Patterns of Summer Precipitation and Circulation Characteristics in Northwest China

<p>In recent years, the summer rainfall shows an increasing trend in Northwest China. Based on the NCEP/NCAR reanalysis data, the RESST data from NOAA and the precipitation data from 351 meteorological observation stations in Northwest China from 1981-2018, the dominant modes of summer precipitation anomalies, the corresponded circulation characteristic and the main influence systems were analyzed by diagnostic methods. There were three dominant EOF modes about summer rainfall, the first one showed the same anomaly in whole region, the second showed a inverse pattern between the east and west, and the third showed the opposite anomaly between the south and north. The variance contribution of the first mode accounted for 20% and the first mode was represented as the primary mode in the subsequent analysis. The high impact region of circulation which affected the precipitation in Northwest China was the middle and high latitudes area of Eurasia and the subtropical area: for the first mode’s positive phase, the 500hPa height field showed a "+ - +" distribution in the middle latitude of Eurasia, while on the 200hPa wind field, there was an anticyclone near the Ural and a cyclone near Lake Baikal, it also has an anticyclone on the Chinese mainland, this configuration will facilitates the strengthening of westerly jets. The tropical Pacific and the North Atlantic are the main external forcing signals of the circulation pattern: SST characteristics showed that the negative phase of the North Atlantic SST Tripole in spring, from winter of the previous year to summer of the current year, SST of the equatorial Middle East Pacific developed from warm to cold. The distribution of 500 hPa height field corresponding to the main mode of summer precipitation in Northwest China is similar to that of EU remote correlation type. An index(I<sub>Hgt</sub>) was defined to reflect circulation patterns in mid-latitude and subtropical regions, when the index is positive/negative, most of the precipitation in northwest China is more/less. After 2000, the correlation between the two increased significantly. Given the performance of the I<sub>Hgt</sub> index in describing the summer precipitation, it could be used as a good indicator in the monitoring and prediction of the summer precipitation in Northwest China.</p>

Subseasonal Midlatitude Prediction Skill Following QBO-MJO Activity

The Madden-Julian Oscillation (MJO) is known to force extratropical weather days-to-weeks following an MJO event through excitation of stationary Rossby waves, tropical-extratropical teleconnections. Prior research has demonstrated that this tropically forced midlatitude response leads to increased prediction skill on subseasonal to seasonal (S2S) timescales. Furthermore, the Quasi-Biennial Oscillation (QBO) has been shown to possibly alter these teleconnections through modulation of the MJO itself and the atmospheric basic state upon which the Rossby waves propagate. This implies that the MJO-QBO relationship may affect midlatitude circulation prediction skill on S2S timescales. In this study, we quantify midlatitude circulation sensitivity and prediction skill following active MJOs and QBOs across the Northern Hemisphere on S2S timescales through an examination of the 500 hPa geopotential height field. First, a comparison of the spatial distribution of Northern Hemisphere sensitivity to the MJO during different QBO phases is performed for ERA-Interim reanalysis and ECMWF and NCEP hindcasts. Secondly, differences in prediction skill in ECMWF and NCEP hindcasts are quantified following MJO-QBO activity. We find that regions across the Pacific, North America and the Atlantic exhibit increased prediction skill following MJO-QBO activity, but these regions are not always collocated with the locations most sensitive to the MJO under a particular QBO state. Both hindcast systems demonstrate enhanced prediction skill 7–14 days following active MJO events during strong QBO periods compared to MJO events during neutral QBO periods.

The Role of Tropical Heating and Internal Variability in the California Response to the 2015/16 ENSO Event

Ensemble reforecast experiments are performed for the boreal winters of 2015/16 (an El Niño year) and 2016/17 in order to understand the origin of the highly unexpected low precipitation over Southern California (SoCal) during 2015/16. The specific hypothesis tested is that the December–March anomalies in (i) SoCal precipitation (highly negative) and (ii) the 200-hPa height field in the Pacific–North American (PNA) region (unusual for an El Niño year) were forced by tropical diabatic heating, as estimated from reanalysis fields. Ten-member ensemble reforecasts for November–March for each year were carried out using the Community Earth System Model and the Climate Forecast System, version 2, models. They were repeated with diabatic heating fields added to the temperature tendencies produced by the models over the tropical Indo-Pacific region throughout the reforecasts. These added fields were obtained from an iterative process that greatly reduces the error in the seasonal mean, trend, and parabolic fit of the model heating (compared to reanalysis estimates). The SoCal precipitation and PNA height field ensemble-mean differences between 2015/16 and 2016/17 for the control and added-heating experiments showed a strong El Niño–like response in both models, including high SoCal precipitation anomalies. Using partial least squares regression to relate variations in SoCal precipitation to the PNA height field within the reforecasts, we further confirm that the observed anomalies are due to noise, and do not constitute a response forced by the seasonal-mean tropical diabatic heating in the Indo-Pacific region.