Monthly Mean Hourly Research Articles

Seasonal changes of the diurnal variation of precipitation in the upper Río Chagres basin, Panamá.

This study elucidated the characteristics of climatological seasonal changes in the diurnal variations of precipitation at four ground stations in the upper Río Chagres basin in the Panama Canal watershed. The seasonal changes differed among the stations, although they are located within an area of only 414 km2. Precipitation peaks in the early afternoon at 1500 local standard time (LST) were observed at all the stations. At Chamon, monthly-mean hourly precipitation at every hour exceeded 0.3 mm h–1 throughout November and December. The occurrence of morning precipitation in January and March distinguished the seasonal precipitation pattern at Esperanza from the pattern at the other stations. Analyses of the seasonal changes in the diurnal variation with pattern correlations and rotational empirical orthogonal functions grouped the stations into two pairs: no morning peak at Chico and Río Piedras in the downstream basin and morning peak at Chamon and Esperanza in the upstream basin.

Evidence of short spatial variability of the equatorial electrojet at close longitudinal separation

The characteristics of longitudinal variability of equatorial electrojet (EEJ) and counter electrojet (CEJ), presented in this study, are based on concurrent observations from a hitherto unsampled region of the world to examine the (1) degree of correlation between hourly means and monthly averaged hourly means of ground observations with equatorial electrojet climatological model (EEJM-2.0), (2) day-to-day longitudinal variability of EEJ strength between the pairs of sites, and (3) longitudinal variability in occurrences of counter electrojet. The analyses are based on the data obtained from an observatory and three new remote sites in the northern Indian Ocean at a longitudinal separation of approximately 15°: Hyderabad (HYB) and Vencode (VEN) at 77° E and Port Blair (PBR) and Campbell Bay (CBY) at 93° E, for a period of 4 months during Lloyd's D-season (November 2011 to February 2012) and comparison with the EEJM-2.0 based on CHAMP satellite data. At both longitudes, the overall correlation of monthly mean hourly values (i.e., from 05:00 to 19:00 LT) between the observed EEJ strength and modeled current density from EEJM-2.0 is good (r > 0.8). However, a significant lack of correlation is witnessed on day-to-day peak values (i.e., 12:00 LT) between the observed variations and the model at both sites. Further, a comparison of noontime peaks between the two sites shows a considerable day-to-day variability. A large number of CEJs (43 events) are recorded during the study: at CBY (15 events) and VEN (28 events). Analyses of the CEJ events highlight the variability of CEJ phenomena in terms of amplitude, dates, and time of occurrence over 15° longitude separation. The local nature of perturbations causing CEJ is evident; the possible factors are being non-migrating eastward and westward propagating diurnal tides and local meteorological phenomena associated with upper mesospheric temperature, wind, and density variations.

Analysis of Solar Direct Irradiance in Spain

Monthly mean hourly (MMH) values of direct irradiance are obtained for different locations in Spain corresponding to different climatic conditions. These values are shown through isolines diagrams. Representative values of direct irradiance for different time of the year and different hour of the day can be easily read from these diagrams. Statistical mean values are obtained from hourly direct irradiance experimental data supplied by the National Meteorological Agency in Spain (AEMET) for the period 2002-2012. Simultaneously, a similar analysis is carried out over the clearness index Kt calculated from hourly experimental data of global irradiance. Monthly mean hourly values of Kt are presented by isolines diagrams representing the behavior of this index along the year. Finally, a correlation between MMH values of direct irradiance and clearness index is analyzed.

The Diffuse Fraction of Global Solar Irradianceat a Tropical Location

The annual and monthly mean diurnal variations of the diffuse fraction of global solar irradiance arriving on the ground at a tropical station in Sub-Sahel Africa is here been reported. The monthly mean hourly values of the diffuse fraction (K d ) for such clear-sky months as February, March and November at this location, which approach a minimum at about local noon, are observed to lie generally below 0.50 during the period from 11:00 to 15:00 hrs (LST). Consequently, solar concentrators utilising parabolic mirrors are expected to have high performance during these months in this region. Like the mainly-cloudy and wet months (June to August) in which monthly mean hourly values of K d higher than 0.62 have been recorded, the corresponding diffuse fraction for dust-haze months (mostly December and January) with high turbidity coefficients were generally above 0.50. Monthly mean hourly values of K d for less cloudy months (April, May, September and October) ranged between 0.48 and 0.77 during the period from 11:00 to 15:00 hrs (LST). The effects of atmospheric dust-haze, clouds and albedo on the monthly mean diurnal variation of the diffuse fraction has been discussed. Also reported are the characteristic values of K d for sets of months with relatively similar atmospheric and sky conditions at this location. The annual variations of the monthly mean daily values of K d which exhibit strong seasonal dependence showed a peak in August for both years. Except for the months of February and March, the monthly mean daily totals of K d exhibited similar annual marches during both years. The major discrepancy in the values of the monthly mean daily totals of K d in both years were recorded in the months of February, November and December, with the corresponding K d values for these months in both years agreeing only to within 32.9% in February, 15.4% in November and 16.2% in December. Apart from the aforementioned months, the corresponding monthly mean daily totals of K d for the remaining nine months in both years agreed mostly to within less than 8.4%. The least monthly mean daily ratios of K d were obtained in the relatively clear month of November for both years being 0.43 in 1993 and 0.49 in 1994. On an annual average, the diffuse component was found to constitute 59.6% of the global solar irradiance arriving on the ground at this region in 1993 and 60.9% in 1994. The results been reported here have been compared with a few others emanating from other tropical stations.

Prediction of monthly-mean hourly relative humidity, ambient temperature, and wind velocity for India

This paper presents a procedure to predict monthly-mean hourly values of relative humidity, ambient temperature and wind velocity for an Indian location. Three maps, showing distribution of annual-average hourly values of humidity, temperature and wind velocities, are prepared from the analysis of available meteorological data of 205 Indian cities. An equation is obtained for annual-average temperature as a function of altitude of the location. Sets of equations are then developed to predict the said weather parameters by the least square regression analysis of the data of 14 cities, taken from different regions, out of 19 cities for which detailed weather data was available. A ratio of monthly-mean to the yearly-mean value of variable is correlated with month and then hourly to the monthly-mean value is correlated with day-hours. On comparison of the computed results with the measured data of the remaining 5 cities, yearly-average relative standard deviations are 14.6, 10.5 and 26.7% for monthly-mean hourly relative humidity, ambient temperature and wind velocities, respectively.

Solar cycle variation of the total electron content around equatorial anomaly crest region in east asia

The monthly mean hourly values of total electron content data obtained at Lunping Observatory (geographic coordinates 25.00°N, 121.17°E; geomagnetic coordinates 14.3°N, 191.3°E) by using the ETS2 satellite beacon signal during the period from March 1977 to December 1990 have been used to analyze the solar cycle variations of total electron content (TEC) around equatorial anomaly crest region in East Asia. Positive, correlations were found between the 12 month running average of monthly mean TECs and sunspot numbers. By using the linear regression analysis method, the contour charts for real diurnal and seasonal variations of TEC at certain sunspot numbers were constructed and described. The diurnal variation of TEC was represented by the sum of its diurnal mean and first three harmonic components. The solar cycle variations of these components have also been discussed.

The Ionosphere at Huancayo, Peru, October to December, 1941

This report is a continuation of those already published in this JOURNAL1 and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionospheric regions as obtained from the automatic multifrequency ionospheric recording apparatus located near Huancayo, Peru, South America, in latitude 12° 02′.7 south, longitude 75° 20′.4 west of Greenwich, which operates over a frequency‐range 0.516 to 16.0 Mc/sec. A complete discussion of these data will be made in an annual summary.Table 1 gives the monthly mean hourly values of the actual heights of maximum electron‐density (hmax), uncorrected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was greater than 0.516 Mc/sec.

The Ionosphere at Watheroo, Western Australia, July to September, 1941

This report is a continuation of those already published in this JOURNAL and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionosphere as obtained by means of automatic multifrequency ionospheric recording apparatus located near Watheroo, Western Australia, in latitude 30° 19′.1 south, longitude 115° 52′.6 east of Greenwich, which operates over the frequency‐range 0.516 to 16.0 Mc/sec.Table 1 gives the monthly mean hourly values of the height of maximum electron‐density (hmax), uncorrected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was higher than 0.5.16 Mc/sec.

The Ionosphere at Huancayo, Peru, July to September, 1941

This report is a continuation of those already published in this JOURNAL and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionospheric.regions as obtained from the automatic multifrequency ionospheric recording apparatus located near Huancayo, Peru, South America, in latitude 12° 02′.7 south, longitude 75° 20′.4 west of Greenwich, which operates over a frequency‐range 0.516 to 16.0 Mc/sec. A complete discussion of these data will be made in an annual summary.Table 1 gives the monthly mean hourly values of the actual heights of maximum electron‐density (hmax), uncorrected for retardation in lower regions2, and the minimum virtual height (hmax) for both the F1‐ and F2‐Vregions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was greater than 0.516 Mc/sec.

The Ionosphere at Watheroo, Western Australia, April to June, 1941

This report is a continuation of those already published in this Journal1 and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionosphere as obtained by means of automatic multifrequency ionospheric recording apparatus located near Watheroo, Western Australia, in latitude 30° 19′.1 south, longitude 115° 52′.6 east of Greenwich, which operates over the frequency‐range 0.516 to 16.0 Mc/sec.Table 1 gives the monthly mean hourly values of the height of maximum electron‐density (hmax), uncorrected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was higher than 0.516 Mc/sec.

The Ionosphere at Huancayo, Peru, April to June, 1941

This report is a continuation of those already published in this Journal1 and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionospheric regions as obtained from the automatic multifrequency ionospheric recording apparatus located near Huancayo, Peru, South America, in latitude 12° 02′.7 south, longitude 75° 20′.4 west of Greenwich, which operates over a frequency‐range 0.516 to 16.0 Mc/sec. A complete discussion of these data will be made in an annual summary.Table 1 gives the monthly mean hourly values of the actual heights of maximum electron‐density (hmax), uncorrected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was greater than 0.516 Mc/sec.

The Ionosphere at Huancayo, Peru, October, 1940, to March, 1941

This report is a continuation of those already published in this Journal1 and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionospheric regions as obtained from the automatic multifrequency ionospheric recording apparatus located near Huancayo, Peru, South America, in latitude 12° 02′.7 south, longitude 75° 20°.4 west of Greenwich, which operates over a frequency‐range 0.516 to 16.0 Mc/sec. A complete discussion of these data will be made in an annual summary.Table 1 gives the monthly mean hourly values of the actual heights of maximum electron‐density (hmax), uncorrected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was greater that 0.516 Mc/sec.

The Ionosphere at Watheroo, Australia, October, 1940, to March, 1941

This report is a continuation of those already published in this Journal1 and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionosphere as obtained by means of automatic multifrequency ionospheric recording apparatus located near Watheroo, Western Australia, in latitude 30° 19′.1 south, longitude 115° 52′.6 east of Greenwich, which operates over the frequency‐range 0.516 to 16.0 Mc/sec.Table 1 gives the monthly mean hourly values of the height of maximum electron‐density (hmax), unconnected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was higher than 0.516 Mc/sec.

The Ionosphere at Huancayo, Peru, July to September, 1940

This report is a continuation of those already published in this Journal1 and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionosphere as obtained by means of automatic multifrequency ionospheric recording apparatus located near Huancayo, Peru, South America, in latitude 12° 02′.7 south, longitude 75° 20′.4 west of Greenwich, which operates over the frequency‐range 0.516 to 16.0 Mc/sec. A complete discussion of these data will be made in an annual summary.Table 1 gives the monthly mean hourly values of the height of maximum electron‐density (hmax), uncorrected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was higher than 0.516 Mc/sec.

The Ionosphere at Watheroo, Western Australia, July to September, 1940

This report is a continuation of those already published in this Journal1 and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionosphere as obtained by means of automatic multifrequency ionospheric recording apparatus located near Watheroo, Western Australia, in latitude 30° 19′.1 south, longitude 115° 52′.6 east of Greenwich, which operates over the frequency‐range 0.516 to 16.0 Mc/sec.Table 1 gives the monthly mean hourly values of the height of maximum electron‐density (hmax), uncorrected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was higher than 0.516 Mc/sec.