Mirjana Ruml - Academia.edu (original) (raw)

Papers by Mirjana Ruml

Acta Horticulturae, 2016

This study examines the impact of harvest date, temperature and precipitation on an accumulation ... more This study examines the impact of harvest date, temperature and precipitation on an accumulation of the volatile aromatic compounds in 'Cabernet Sauvignon' wine. The research was carried out in the vineyard of King Peter I Karadjordjevic, the Royal Winery in Oplenac, Serbia, during 2010 and 2011. In each year grapes were harvested twice-when the full maturity has been reached and 15 days later. Aromatic complexes of these 4 wines were analyzed using the Gas Chromatography Mass Spectrometry (GC-MS) and the Gas Chromatography with Flame Ionization Detector (GC-FID). Higher alcohols, lactones, organic acids, esters and amides were detected in wines. Relative portions of 34 aromatic compounds were compared for the full maturity harvests in the both experimental years, as well as their change from the first to the second harvest in each year.

Annals of the University of Craiova - Agriculture, Montanology, Cadastre Series, 2014

Research carried out in vineyard of King Peter I Karadjordjevic-Royal Winery at Oplenac-Topola mu... more Research carried out in vineyard of King Peter I Karadjordjevic-Royal Winery at Oplenac-Topola municipality, on Sauvignon blanc and Cabernet sauvignon. Vineyard planted with Sauvignon blanc is geographically positioned at GPS coordinates N 44° 14' 4" and E 20° 41' 15" and Cabernet sauvignon is geographically positioned at GPS coordinates N 44° 14' 35" and E 20° 41' 22". Climat parameters (series from 1982-2011 year) included following parameters: mean monthly, vegetation (april-october) and annual temperature, active and effective temperature, precipitation distribution (annual and vegetation) and wind direction. Phenological observation included beginning and end of following phenophases: bleeding, budbreakt, shoot growing, flowering, berry development and ripening. The greatest variation Sauvignon blanc manifested in duration of grape ripening which is in 2010. lasted 46 days while in 2011. lasted 34 days. Cabernet sauvignon in 2011. had a lower...

The adequate choice of suitable cultivar/clone together with the ecological characteristics of th... more The adequate choice of suitable cultivar/clone together with the ecological characteristics of the region and combination of agro technical measures represents the most important factors in the viticulture production. Aim of this study was to determine the characteristics of two Pinot Noir clones (R4 and 667) in two Serbian grape growing regions with different meteorological conditions. The following properties were investigated: beginning, end and length of the growing season, grape yield, mechanical composition of bunch and berry, grape and wine quality. Differences between studied 'Pinot Noir' clones and environmental conditions in grape growing regions resulted in the production of grapes and wine with different characteristics.

Theoretical and Applied Climatology

This paper documents the change of temperature indices for the growing season (April–September) a... more This paper documents the change of temperature indices for the growing season (April–September) and dormancy (October–March) in Serbia based on observations from 26 meteorological stations. The mean, maximum, and minimum daily temperatures, as well as eight extreme temperature indices, were examined. A trend analysis revealed uneven changes in the growing season and dormant temperatures during the observation period divided into two parts (1961–1980 and 1981–2010) according to the results of the sequential Mann–Kendall test for detecting change points in time series. The dormant temperature changes were quite uniform during the entire examined period, while the growing season temperature displayed a complex pattern of change. In the sub-period 1961–1980, all examined temperature indices exhibited a cooling tendency during the growing season and a warming tendency during dormancy. A larger decreasing trend was detected in the growing season maximum temperature (a nationally averaged rate − 1.10 °C per decade) and related indices than in the growing season minimum temperature (a nationally averaged rate − 0.37 °C per decade) and related indices. In the same sub-period, the dormant maximum and minimum temperatures increased at the same rate of 0.49 °C per decade on average for all stations. During the sub-period 1981–2010, a warming tendency was detected both in the growing season and dormant temperature indices with similar magnitudes of the change (minimum and maximum temperatures increased on average from 0.48 to 0.56 °C per decade). Examination of the relationship between the temperature indices and large-scale circulation patterns revealed that only the East Atlantic pattern displayed significant association with trends of examined indices, but only during the growing season in the sub-period 1981–2010.

Regulated deficit irrigation (RDI) is a water-saving irrigation method that is now undergoing ext... more Regulated deficit irrigation (RDI) is a water-saving irrigation method that is now undergoing extensive trials worldwide but novel for Serbia and other countries of South East European region. In order to asses the possible application of RDI method in climate conditions of South East European region, the experiments were carried out in vineyard (variety Riesling) and RDI plants received ca. 60% of the water that was applied to fully irrigated (FI) plants. Thus, the significant amount of water for irrigation was saved. Data concerning yield and the soluble solids in the berries did not showed significant differences between RDI and FI plants, while the titrable acidity and antioxidant activity in the berries and IWUE were significantly increased under RDI. Economic analyses was also done to asses the effect of RDI on profit of grape production.Redukovano navodnjavanje (RDI) je metoda kojom se može uštedeti voda za navodnjavanje i koja se intenzivno upotrebljava u svetu, ali je nova ...

The study aimed to evaluate changes in wine grape yield and composition in response to observed w... more The study aimed to evaluate changes in wine grape yield and composition in response to observed warming and advanced phenology in the region of Sremski Karlovci over last few decades. The analysis was based on long-term observations (1986–2007) of temperature, phenology, yield, grape cluster mass, sugar content and total acidity in the must for Riesling Italian and Lemberger, the most common grape varieties in the studied region. A significant temporal trend was observed only for yield in Riesling Italian, while in Limberger, both yield and grape cluster mass showed significant positive change over time. The yield in both varieties was most affected and positively correlated with warm growing season of preharvest year. For sugar content in the must, the most influential temperature variable was growing season diurnal temperature range in Riesling Italian, while in Limberger that was diurnal temperature range during ripening. The number of warm days (maximum daily temperature >90t...

An analysis of recent-past changes in grapevine phenology in the region of Sremski Karlovci was p... more An analysis of recent-past changes in grapevine phenology in the region of Sremski Karlovci was performed. The study was based on 26 years of observations (1986–2011) on beginning of budburst, beginning of flowering, beginning of veraison and harvest for 21 different vine cultivars. The study revealed a trend toward earlier occurrence of phenological events for all cultivars. However not all the phenological events responded to changes in the environment to the same extent and with the same level of significance. Trends of –0.4, –0.7 and –0.6 days/year were detected for the phenological dates averaged over all examined cultivars for the beginning of flowering, beginning of veraison, and harvest dates, respectively. Beginning of budburst exhibited no significant trend during studied period. The trend comparison between cultivars revealed that harvest dates of early and middle ripening cultivars were advancing somewhat more than dates of late ripening cultivars.

The study aimed to evaluate the structure, variability and trends of climate parameters important... more The study aimed to evaluate the structure, variability and trends of climate parameters important for grapevine growing in Sremski Karlovci for the period 1981–2007. A number of average and extreme temperature indices were calculated for annual, growing season and different growth intervals of grapevine. Results showed significant trends in: annual mean, maximum and minimum temperatures (0.06, 0.06 and 0.05°C/year, respectively); growing season mean, maximum and minimum temperatures (0.04, 0.05 and 0.05°C/year, respectively); growing degree days (10.7°C/year); annual number of days with minimum temperature higher than 90th percentile (1.0 days/year); annual number of days with maximum temperature higher than 90th percentile (0.9 days/year); the number of days with maximum temperatures above 30°C (0.7 days/year) and the number of days with maximum temperatures above 35°C (0.2 days/year); the number of tropical nights (0.6 days/year); the number of days with minimum temperatures below...

Acta Horticulturae, 2018

High year-to-year apricot yield oscillations in Serbia are mostly caused by late spring frost. Th... more High year-to-year apricot yield oscillations in Serbia are mostly caused by late spring frost. Thus, phenological prediction can help to get more stable apricot yields providing dates for timely frost protection. This study aimed to validate a feasible, easy to apply model for prediction of full flowering in apricot cultivars based on air temperature averaged over 30-, 45-and 60-day periods starting from January 1. The model, capable of predicting the onset of full flowering in apricot cultivars from a few weeks to up to two months ahead with acceptable accuracy, was originally developed using phenological data for 20 apricot cultivars grown in the Belgrade region and daily temperature records over the period 1995-2004. Reevaluation of the data set consisted of phenological records for 20 cultivars grown in the same region and temperature observations from 2009 to 2016. The mean absolute differences between the observations and predictions obtained by 30-, 45-and 60-day models were 5.5, 6.4 and 5.6 days, respectively, on average for all examined cultivars.

Acta Horticulturae, 2016

Heat requirements for four major phenological stages (budburst, flowering, veraison and harvest) ... more Heat requirements for four major phenological stages (budburst, flowering, veraison and harvest) were assessed in eight red grapevine cultivars grown in the Sremski Karlovci region in northern Serbia using a growing degree-days (GDD) method and base temperature of 10°C. Temperature and phenological data covering the period 1986-2007 were used to conduct the study. The accumulated GDD for the beginning of budburst ranged from 70 ('Gamay' and 'Limberger') to 92 ('Cabernet Sauvignon'). The heat requirements for the beginning of flowering varied between 338 GDD in 'Gamay' to 398 GDD in 'Probus'. The smallest heat requirements to reach the beginning of veraison was observed in 'Portugizer' (937 GDD) and the greatest in 'Probus' (1117 GDD). The GDD for harvest spanned the range from 1555 in 'Portugizer' to 1649 in 'Prokupac'. Generally, a greater variation in GDD was found between years for a single cultivar than among cultivars within individual years. Among phenological stages, the greatest inter-annul variation in terms of coefficient of variation was displayed for the beginning of budburst and the least for harvest.

Acta Horticulturae, 2012

Heat requirement for flowering in apricot cultivars was estimated from field data using Growing D... more Heat requirement for flowering in apricot cultivars was estimated from field data using Growing Degree Days method (GDD). Ten years of phenological and temperature data for 42 apricot cultivars of diverse geographical origin and different flowering time, grown in Belgrade region, were used to conduct the study. Base temperatures for different cultivars were obtained by the RMSE (the smallest root mean square error between the observed and predicted number of days) method. The base temperatures calculated by this method differed among cultivars from-2.8 to 0.2°C. GDD was calculated from 1 January to the beginning of flowering using base temperatures obtained by RMSE method, the Null method (base temperature set to 0°C for all cultivars) and Fixed Value method (base temperature set to-1°C for all cultivars). The best agreement with observations in terms of mean absolute error (MAE) was attained by RMSE method (MAE= 2.7 days). However, the Null method (MAE=3.2 days) and Fixed Value method (MAE=3.0 days) gave also very good results. Taking-1°C for the base temperature (the mean value of all cultivars studied), the accumulated GDD for flowering varied from 332 (in 'Tyrinthos') to 425 (in 'Stella').

The study aimed to evaluate spatiotemporal changes of temperature and precipitation in Serbia usi... more The study aimed to evaluate spatiotemporal changes of temperature and precipitation in Serbia using observations from 26 meteorological stations over the period 1961-2010. Temporal trends were determined by a least-squares linear regression method for each station and for the entire Serbian territory using the average series for the periods 1961-2010 and 1986-2010. It was found that both minimum and maximum temperatures had significantly increased in Serbia, with the greater magnitude in the recent-past. Annual precipitation has not displayed significant change over the entire period. In the more recent period, a lager increase in precipitation was recorded, significant at a greater number of stations.

Thermal requirements to reachbudburst, flowering, veraison and harvest for thirteenwhite grapevin... more Thermal requirements to reachbudburst, flowering, veraison and harvest for thirteenwhite grapevine varieties grown in the Sremski Karlovci region were determined using a growing degree-days (GDD) method and base temperature of 10°C. The accumulated GDD for the beginning of budburst ranged from 60 ('Petra') to 79 ('Bagrina'). The thermal requirements for the beginning flowering varied between 334 GDD in 'Chardonnay' to 404 GDD in 'Bagrina'. The smallest accumulated GDD to reach the beginning of veraison was observed in 'Bouvier' (869) and the greatest in'Riesling Italian' (1106). The GDD for harvest spanned the range from 1530 in 'Muscat Ottonel' to 1717 in 'Riesling Italian'. Greater variation in GDD was displayed between years for a single variety than among varieties within individual years. Considering phenological stages, the greatest year-to-year variability was found for the beginning of budburst and the least for harvest.

Climate Research, 2017

Table S1. Mathematical definition and classes of bioclimatic indices used in the study Bioclimati... more Table S1. Mathematical definition and classes of bioclimatic indices used in the study Bioclimatic index Definition Classes References Growing season mean temperature

Acta Horticulturae, 2016

This study examines the impact of harvest date, temperature and precipitation on an accumulation ... more This study examines the impact of harvest date, temperature and precipitation on an accumulation of the volatile aromatic compounds in 'Cabernet Sauvignon' wine. The research was carried out in the vineyard of King Peter I Karadjordjevic, the Royal Winery in Oplenac, Serbia, during 2010 and 2011. In each year grapes were harvested twice-when the full maturity has been reached and 15 days later. Aromatic complexes of these 4 wines were analyzed using the Gas Chromatography Mass Spectrometry (GC-MS) and the Gas Chromatography with Flame Ionization Detector (GC-FID). Higher alcohols, lactones, organic acids, esters and amides were detected in wines. Relative portions of 34 aromatic compounds were compared for the full maturity harvests in the both experimental years, as well as their change from the first to the second harvest in each year.

Annals of the University of Craiova - Agriculture, Montanology, Cadastre Series, 2014

Research carried out in vineyard of King Peter I Karadjordjevic-Royal Winery at Oplenac-Topola mu... more Research carried out in vineyard of King Peter I Karadjordjevic-Royal Winery at Oplenac-Topola municipality, on Sauvignon blanc and Cabernet sauvignon. Vineyard planted with Sauvignon blanc is geographically positioned at GPS coordinates N 44° 14' 4" and E 20° 41' 15" and Cabernet sauvignon is geographically positioned at GPS coordinates N 44° 14' 35" and E 20° 41' 22". Climat parameters (series from 1982-2011 year) included following parameters: mean monthly, vegetation (april-october) and annual temperature, active and effective temperature, precipitation distribution (annual and vegetation) and wind direction. Phenological observation included beginning and end of following phenophases: bleeding, budbreakt, shoot growing, flowering, berry development and ripening. The greatest variation Sauvignon blanc manifested in duration of grape ripening which is in 2010. lasted 46 days while in 2011. lasted 34 days. Cabernet sauvignon in 2011. had a lower...

The adequate choice of suitable cultivar/clone together with the ecological characteristics of th... more The adequate choice of suitable cultivar/clone together with the ecological characteristics of the region and combination of agro technical measures represents the most important factors in the viticulture production. Aim of this study was to determine the characteristics of two Pinot Noir clones (R4 and 667) in two Serbian grape growing regions with different meteorological conditions. The following properties were investigated: beginning, end and length of the growing season, grape yield, mechanical composition of bunch and berry, grape and wine quality. Differences between studied 'Pinot Noir' clones and environmental conditions in grape growing regions resulted in the production of grapes and wine with different characteristics.

Theoretical and Applied Climatology

This paper documents the change of temperature indices for the growing season (April–September) a... more This paper documents the change of temperature indices for the growing season (April–September) and dormancy (October–March) in Serbia based on observations from 26 meteorological stations. The mean, maximum, and minimum daily temperatures, as well as eight extreme temperature indices, were examined. A trend analysis revealed uneven changes in the growing season and dormant temperatures during the observation period divided into two parts (1961–1980 and 1981–2010) according to the results of the sequential Mann–Kendall test for detecting change points in time series. The dormant temperature changes were quite uniform during the entire examined period, while the growing season temperature displayed a complex pattern of change. In the sub-period 1961–1980, all examined temperature indices exhibited a cooling tendency during the growing season and a warming tendency during dormancy. A larger decreasing trend was detected in the growing season maximum temperature (a nationally averaged rate − 1.10 °C per decade) and related indices than in the growing season minimum temperature (a nationally averaged rate − 0.37 °C per decade) and related indices. In the same sub-period, the dormant maximum and minimum temperatures increased at the same rate of 0.49 °C per decade on average for all stations. During the sub-period 1981–2010, a warming tendency was detected both in the growing season and dormant temperature indices with similar magnitudes of the change (minimum and maximum temperatures increased on average from 0.48 to 0.56 °C per decade). Examination of the relationship between the temperature indices and large-scale circulation patterns revealed that only the East Atlantic pattern displayed significant association with trends of examined indices, but only during the growing season in the sub-period 1981–2010.

Regulated deficit irrigation (RDI) is a water-saving irrigation method that is now undergoing ext... more Regulated deficit irrigation (RDI) is a water-saving irrigation method that is now undergoing extensive trials worldwide but novel for Serbia and other countries of South East European region. In order to asses the possible application of RDI method in climate conditions of South East European region, the experiments were carried out in vineyard (variety Riesling) and RDI plants received ca. 60% of the water that was applied to fully irrigated (FI) plants. Thus, the significant amount of water for irrigation was saved. Data concerning yield and the soluble solids in the berries did not showed significant differences between RDI and FI plants, while the titrable acidity and antioxidant activity in the berries and IWUE were significantly increased under RDI. Economic analyses was also done to asses the effect of RDI on profit of grape production.Redukovano navodnjavanje (RDI) je metoda kojom se može uštedeti voda za navodnjavanje i koja se intenzivno upotrebljava u svetu, ali je nova ...

The study aimed to evaluate changes in wine grape yield and composition in response to observed w... more The study aimed to evaluate changes in wine grape yield and composition in response to observed warming and advanced phenology in the region of Sremski Karlovci over last few decades. The analysis was based on long-term observations (1986–2007) of temperature, phenology, yield, grape cluster mass, sugar content and total acidity in the must for Riesling Italian and Lemberger, the most common grape varieties in the studied region. A significant temporal trend was observed only for yield in Riesling Italian, while in Limberger, both yield and grape cluster mass showed significant positive change over time. The yield in both varieties was most affected and positively correlated with warm growing season of preharvest year. For sugar content in the must, the most influential temperature variable was growing season diurnal temperature range in Riesling Italian, while in Limberger that was diurnal temperature range during ripening. The number of warm days (maximum daily temperature >90t...

An analysis of recent-past changes in grapevine phenology in the region of Sremski Karlovci was p... more An analysis of recent-past changes in grapevine phenology in the region of Sremski Karlovci was performed. The study was based on 26 years of observations (1986–2011) on beginning of budburst, beginning of flowering, beginning of veraison and harvest for 21 different vine cultivars. The study revealed a trend toward earlier occurrence of phenological events for all cultivars. However not all the phenological events responded to changes in the environment to the same extent and with the same level of significance. Trends of –0.4, –0.7 and –0.6 days/year were detected for the phenological dates averaged over all examined cultivars for the beginning of flowering, beginning of veraison, and harvest dates, respectively. Beginning of budburst exhibited no significant trend during studied period. The trend comparison between cultivars revealed that harvest dates of early and middle ripening cultivars were advancing somewhat more than dates of late ripening cultivars.

The study aimed to evaluate the structure, variability and trends of climate parameters important... more The study aimed to evaluate the structure, variability and trends of climate parameters important for grapevine growing in Sremski Karlovci for the period 1981–2007. A number of average and extreme temperature indices were calculated for annual, growing season and different growth intervals of grapevine. Results showed significant trends in: annual mean, maximum and minimum temperatures (0.06, 0.06 and 0.05°C/year, respectively); growing season mean, maximum and minimum temperatures (0.04, 0.05 and 0.05°C/year, respectively); growing degree days (10.7°C/year); annual number of days with minimum temperature higher than 90th percentile (1.0 days/year); annual number of days with maximum temperature higher than 90th percentile (0.9 days/year); the number of days with maximum temperatures above 30°C (0.7 days/year) and the number of days with maximum temperatures above 35°C (0.2 days/year); the number of tropical nights (0.6 days/year); the number of days with minimum temperatures below...

Acta Horticulturae, 2018

High year-to-year apricot yield oscillations in Serbia are mostly caused by late spring frost. Th... more High year-to-year apricot yield oscillations in Serbia are mostly caused by late spring frost. Thus, phenological prediction can help to get more stable apricot yields providing dates for timely frost protection. This study aimed to validate a feasible, easy to apply model for prediction of full flowering in apricot cultivars based on air temperature averaged over 30-, 45-and 60-day periods starting from January 1. The model, capable of predicting the onset of full flowering in apricot cultivars from a few weeks to up to two months ahead with acceptable accuracy, was originally developed using phenological data for 20 apricot cultivars grown in the Belgrade region and daily temperature records over the period 1995-2004. Reevaluation of the data set consisted of phenological records for 20 cultivars grown in the same region and temperature observations from 2009 to 2016. The mean absolute differences between the observations and predictions obtained by 30-, 45-and 60-day models were 5.5, 6.4 and 5.6 days, respectively, on average for all examined cultivars.

Acta Horticulturae, 2016

Heat requirements for four major phenological stages (budburst, flowering, veraison and harvest) ... more Heat requirements for four major phenological stages (budburst, flowering, veraison and harvest) were assessed in eight red grapevine cultivars grown in the Sremski Karlovci region in northern Serbia using a growing degree-days (GDD) method and base temperature of 10°C. Temperature and phenological data covering the period 1986-2007 were used to conduct the study. The accumulated GDD for the beginning of budburst ranged from 70 ('Gamay' and 'Limberger') to 92 ('Cabernet Sauvignon'). The heat requirements for the beginning of flowering varied between 338 GDD in 'Gamay' to 398 GDD in 'Probus'. The smallest heat requirements to reach the beginning of veraison was observed in 'Portugizer' (937 GDD) and the greatest in 'Probus' (1117 GDD). The GDD for harvest spanned the range from 1555 in 'Portugizer' to 1649 in 'Prokupac'. Generally, a greater variation in GDD was found between years for a single cultivar than among cultivars within individual years. Among phenological stages, the greatest inter-annul variation in terms of coefficient of variation was displayed for the beginning of budburst and the least for harvest.

Acta Horticulturae, 2012

Heat requirement for flowering in apricot cultivars was estimated from field data using Growing D... more Heat requirement for flowering in apricot cultivars was estimated from field data using Growing Degree Days method (GDD). Ten years of phenological and temperature data for 42 apricot cultivars of diverse geographical origin and different flowering time, grown in Belgrade region, were used to conduct the study. Base temperatures for different cultivars were obtained by the RMSE (the smallest root mean square error between the observed and predicted number of days) method. The base temperatures calculated by this method differed among cultivars from-2.8 to 0.2°C. GDD was calculated from 1 January to the beginning of flowering using base temperatures obtained by RMSE method, the Null method (base temperature set to 0°C for all cultivars) and Fixed Value method (base temperature set to-1°C for all cultivars). The best agreement with observations in terms of mean absolute error (MAE) was attained by RMSE method (MAE= 2.7 days). However, the Null method (MAE=3.2 days) and Fixed Value method (MAE=3.0 days) gave also very good results. Taking-1°C for the base temperature (the mean value of all cultivars studied), the accumulated GDD for flowering varied from 332 (in 'Tyrinthos') to 425 (in 'Stella').

The study aimed to evaluate spatiotemporal changes of temperature and precipitation in Serbia usi... more The study aimed to evaluate spatiotemporal changes of temperature and precipitation in Serbia using observations from 26 meteorological stations over the period 1961-2010. Temporal trends were determined by a least-squares linear regression method for each station and for the entire Serbian territory using the average series for the periods 1961-2010 and 1986-2010. It was found that both minimum and maximum temperatures had significantly increased in Serbia, with the greater magnitude in the recent-past. Annual precipitation has not displayed significant change over the entire period. In the more recent period, a lager increase in precipitation was recorded, significant at a greater number of stations.

Thermal requirements to reachbudburst, flowering, veraison and harvest for thirteenwhite grapevin... more Thermal requirements to reachbudburst, flowering, veraison and harvest for thirteenwhite grapevine varieties grown in the Sremski Karlovci region were determined using a growing degree-days (GDD) method and base temperature of 10°C. The accumulated GDD for the beginning of budburst ranged from 60 ('Petra') to 79 ('Bagrina'). The thermal requirements for the beginning flowering varied between 334 GDD in 'Chardonnay' to 404 GDD in 'Bagrina'. The smallest accumulated GDD to reach the beginning of veraison was observed in 'Bouvier' (869) and the greatest in'Riesling Italian' (1106). The GDD for harvest spanned the range from 1530 in 'Muscat Ottonel' to 1717 in 'Riesling Italian'. Greater variation in GDD was displayed between years for a single variety than among varieties within individual years. Considering phenological stages, the greatest year-to-year variability was found for the beginning of budburst and the least for harvest.

Climate Research, 2017

Table S1. Mathematical definition and classes of bioclimatic indices used in the study Bioclimati... more Table S1. Mathematical definition and classes of bioclimatic indices used in the study Bioclimatic index Definition Classes References Growing season mean temperature