Sudden Commencements and Impulses in Kodaikanal magnetograms -their hourly frequency

The diurnal variation in the frequencies of sudden commencements (SCs) and sudden impulses (SIs) at Kodaikanal (10.2°N, 77.5°E) is analysed from the data for the period 1949-1957.The hourly frequency curve of SCs and SIs (combined) has little resemblance to the curve obtained by Newton from his analysis of Greenwich-Abinger record. The results of harmonic analysis show a nearly semi-diurnal trend the distribution of storm sudden commencements (SSCs); this, however, is small. The hourly frequencies of SIS show s significant diurnal variation with an afternoon maximum and a forenoon maximum and a secondary minimum around 18h local time and a secondary maximum around 08h. These results are also compared with those obtained by Ferraro Parkinson and Unthank.

MIPAS observations of ozone in the middle atmosphere

In this paper we describe the stratospheric and mesospheric ozone (version V5r_O3_m22) distributions retrieved from MIPAS observations in the three middle atmosphere modes (MA, NLC, and UA) taken with an unapodized spectral resolution of 0.0625 cm−1 from 2005 until April 2012. O3 is retrieved from microwindows in the 14.8 and 10 µm spectral regions and requires non-local thermodynamic equilibrium (non-LTE) modelling of the O3 v1 and v3 vibrational levels. Ozone is reliably retrieved from 20 km in the MA mode (40 km for UA and NLC) up to ∼ 105 km during dark conditions and up to ∼ 95 km during illuminated conditions. Daytime MIPAS O3 has an average vertical resolution of 3–4 km below 70 km, 6–8 km at 70–80 km, 8–10 km at 80–90, and 5–7 km at the secondary maximum (90–100 km). For nighttime conditions, the vertical resolution is similar below 70 km and better in the upper mesosphere and lower thermosphere: 4–6 km at 70–100 km, 4–5 km at the secondary maximum, and 6–8 km at 100–105 km. The noise error for daytime conditions is typically smaller than 2 % below 50 km, 2–10 % between 50 and 70 km, 10–20 % at 70–90 km, and ∼ 30 % above 95 km. For nighttime, the noise errors are very similar below around 70 km but significantly smaller above, being 10–20 % at 75–95 km, 20–30 % at 95–100 km, and larger than 30 % above 100 km. The additional major O3 errors are the spectroscopic data uncertainties below 50 km (10–12 %) and the non-LTE and temperature errors above 70 km. The validation performed suggests that the spectroscopic errors below 50 km, mainly caused by the O3 air-broadened half-widths of the v2 band, are overestimated. The non-LTE error (including the uncertainty of atomic oxygen in nighttime) is relevant only above ∼ 85 km with values of 15–20 %. The temperature error varies from ∼ 3 % up to 80 km to 15–20 % near 100 km. Between 50 and 70 km, the pointing and spectroscopic errors are the dominant uncertainties. The validation performed in comparisons with SABER, GOMOS, MLS, SMILES, and ACE-FTS shows that MIPAS O3 has an accuracy better than 5 % at and below 50 km, with a positive bias of a few percent. In the 50–75 km region, MIPAS O3 has a positive bias of ≈ 10 %, which is possibly caused in part by O3 spectroscopic errors in the 10 µm region. Between 75 and 90 km, MIPAS nighttime O3 is in agreement with other instruments by 10 %, but for daytime the agreement is slightly larger, ∼ 10–20 %. Above 90 km, MIPAS daytime O3 is in agreement with other instruments by 10 %. At night, however, it shows a positive bias increasing from 10 % at 90 km to 20 % at 95–100 km, the latter of which is attributed to the large atomic oxygen abundance used. We also present MIPAS O3 distributions as function of altitude, latitude, and time, showing the major O3 features in the middle and upper mesosphere. In addition to the rapid diurnal variation due to photochemistry, the data also show apparent signatures of the diurnal migrating tide during both day- and nighttime, as well as the effects of the semi-annual oscillation above ∼ 70 km in the tropics and mid-latitudes. The tropical daytime O3 at 90 km shows a solar signature in phase with the solar cycle.

MIPAS Observations of Ozone in the Middle Atmosphere

In this paper we describe the stratospheric and mesospheric ozone (version V5r_O3_m22) distributions retrieved from MIPAS observations in the three middle atmosphere modes (MA, NLC and UA) taken with an unapodized spectral resolution of 0.0625 cm−1 from 2005 until April 2012. O3 is retrieved from microwindows in the 14.8 μm and 10 μm spectral regions and requires non-LTE modelling of the O3 v1 and v3 vibrational levels. Ozone is reliably retrieved from 20 km in the MA mode (40 km for UA and NLC) up to ~ 105 km during dark conditions and up to ~ 95 km during illuminated conditions. Daytime MIPAS O3 has an average vertical resolution of 3–4 km below 70 km, 6–8 km at 70–80 km, 8–10 km at 80–90 km and 5–7 km at the secondary maximum (90–100 km). For nighttime conditions the vertical resolution is similar below 70 km, and better in the upper mesosphere and lower thermosphere: 4–6 km at 70–100 km, 4–5 km at the secondary maximum, and 6–8 km at 100–105 km. The noise error for daytime conditions is typically smaller than 2 % below 50 km, 2–10 % between 50 and 70 km, 10–20 % at 70–90 km and ~ 30 % above 95 km. For nighttime, the noise errors are very similar below around 70 km but significantly smaller above, being 10–20 % at 75–95 km, 20–30 % at 95–100 km and larger than 30 % above 100 km. The additional major O3 errors are the spectroscopic data uncertainties below 50 km (10–12 %), and the non-LTE and temperature errors above 70 km. The validation performed suggests that the spectroscopic errors below 50 km, mainly caused by the O3 air-broadened half-widths of the v2 band, are overestimated. The non-LTE error (including the uncertainty of atomic oxygen at nighttime) is relevant only above ~ 85 km with values of 15–20 %. The temperature error varies from ~ 3 % up to 80 km to 15–20 % near 100 km. Between 50 and 70 km, the pointing and spectroscopic errors are the dominant uncertainties. The validation performed in comparisons with SABER, GOMOS, MLS, SMILES and ACE-FTS shows that MIPAS O3 has an accuracy better than 5 % at and below 50 km, with a positive bias of a few percent. In the 50–75 km region, MIPAS O3 has a positive bias of ~ 10 %, which is possibly caused in part by O3 spectroscopic errors in the 10 μm region. Between 75 and 90 km, MIPAS nighttime O3 is in agreement with other instruments by 10 %, but for daytime the agreement is slightly larger, ~ 10–20 %. Above 90 km, MIPAS daytime O3 is in agreement with other instruments by 10 %. At nighttime, however, it shows a positive bias increasing from 10 % at 90 km to 20 % at 95–100 km, the latter of which is attributed to the large atomic oxygen abundance used. We also present MIPAS O3 distributions as function of altitude, latitude and time, showing the major O3 features in the middle and upper mesosphere. In addition to the rapid diurnal variation due to photochemistry, the data also show apparent signatures of the diurnal migrating tide, both during day and nighttime, as well as the effects of the semi-annual oscillation above ~ 70 km in the tropics and mid-latitudes. The tropical daytime O3 at 90 km shows a solar signature in phase with the solar cycle.

Comparison of lightning activity in the two most active areas of the Congo Basin

A comparison of the lightning activity in the two most active areas (Area_max for the main maximum and Area_sec for the secondary maximum) in the Congo Basin is made with data obtained by the WWLLN during 2012 and 2013. Both areas of same size (5° × 5°) exhibit flash counts in a ratio of about 1.32 for both years and very different distributions of the flash density with maximum in a ratio of 1.941 and 2.585 for 2012 and 2013, respectively. The diurnal cycle is much more pronounced in Area_max than in Area_sec with a ratio between the maximum and the minimum of 15.4 and 4.7, respectively. However, the minimum and maximum of the hourly flash rates are observed roughly at the same time in both areas, between 07:00 and 09:00 UTC and between 16:00 and 17:00 UTC, respectively. In Area_sec the number of days with very low activity (0–1000 flashes per day) is very large (164 days) and that with larger activity decreases very rapidly. In Area_max the number of day decreases more slowly and is larger for most of levels of lightning activity. The correlation at the daily scale between the lightning activity in Area_max and that in Area_sec is weak but positive. In summary, the thunderstorm activity in Area_sec is more variable at different scales of time (monthly and daily), in intensity and in location.

Varijabilnost padalina u Hvaru i Crikvenici

The study analyses the precipitation variability in Hvar and Crikvenica in the period from 1931 to 1990. These stations have a maritime type of the annual course of precipitation. The minimum value of the precipitation variability in Hvar is in autumn, in November, while the secondary minimum of the variability is in spring, in April. The primary maximum of variability is in summer, most often in July, while the secondary maximum is in March. In Crikvenica the minimum values of the precipitation variability in April and November are even, and the same is true for the maximum values of the variability in September and March. The value of the annual precipitation variability is higher in Crikvenica than in Hvar although Crikvenica has higher amount of precipitation. The location of the stations included in this research is relevant. In Crikvenica the variability is higher in autumn and winter. Monthly values of the mean relative variability coincide in the cold part of the year when the variability is only slightly higher in Crikvenica, while in the warm part of the year, with the exception of September, the variability in Hvar is significantly higher.

Tornado Climatology of Turkey

A climatology of tornadoes in Turkey is presented using records from a wide variety of sources (e.g., the Turkish State Meteorological Service, European Severe Weather Database, newspaper archives, Internet searches, etc.). The climatology includes the annual, diurnal, geographical, and intensity distributions of both mesocyclonic and nonmesocyclonic tornadoes. From 1818 to 2013, 385 tornado cases were obtained. The tornadoes range from F0 to F3, with F1 being the most frequently reported or inferred intensity. Mesocyclonic tornadoes are most likely in May and June, and a secondary maximum in frequency is present in October and November. Nonmesocyclonic tornadoes (waterspouts) are most common in the winter along the (southern) Mediterranean coast and in the fall along the Black Sea (northern) coast. Tornadoes (both mesocyclonic and nonmesocyclonic) are most likely in the afternoon and early evening hours.

Aerosol particle number size distributions and particulate light absorption at the ZOTTO tall tower (Siberia), 2006–2009

This paper analyses aerosol particle number size distributions, particulate absorption at 570 nm wavelength and carbon monoxide (CO) measured between September 2006 and January 2010 at heights of 50 and 300 m at the Zotino Tall Tower Facility (ZOTTO) in Siberia (60.8° N; 89.35° E). Average number, surface and volume concentrations are broadly comparable to former studies covering shorter observation periods. Fits of multiple lognormal distributions yielded three maxima in probability distribution of geometric mean diameters in the Aitken and accumulation size range and a possible secondary maximum in the nucleation size range below 25 nm. The seasonal cycle of particulate absorption shows maximum concentrations in high winter (December) and minimum concentrations in mid-summer (July). The 90th percentile, however, indicates a secondary maximum in July/August that is likely related to forest fires. The strongly combustion derived CO shows a single winter maximum and a late summer minimum, albeit with a considerably smaller seasonal swing than the particle data due to its longer atmospheric lifetime. Total volume and even more so total number show a more complex seasonal variation with maxima in winter, spring, and summer. A cluster analysis of back trajectories and vertical profiles of the pseudo-potential temperature yielded ten clusters with three levels of particle number concentration: Low concentrations in Arctic air masses (400–500 cm−3), mid-level concentrations for zonally advected air masses from westerly directions between 55° and 65° N (600–800 cm−3), and high concentrations for air masses advected from the belt of industrial and population centers in Siberia and Kazakhstan (1200 cm−3). The observational data is representative for large parts of the troposphere over Siberia and might be particularly useful for the validation of global aerosol transport models.

Aerosol particle number size distributions and particulate light absorption at the ZOTTO tall tower (Siberia), 2006–2009

This paper covers measurements of the number-size distribution of aerosol particles, particulate absorption at 570 nm wavelength and CO as tracer gas from 2006 through 2009 at 50 and 300 m on the ZOTTO tower, Siberia at 60.8° N; 89.35° E. Average number, surface and volume concentrations are similar to results given for continental and boreal background locations. When fitted with lognormal functions, the probability distribution function of modal diameters shows three main maxima in the Aitken and accumulation size range and a possible secondary maximum in the nucleation size range below 25 nm. The seasonal distributions of the different particle parameters differ substantially. Particulate absorption has a clear single maximum in high winter and minimum values in mid-summer. The 90%-percentile, however, indicates a possible secondary maximum in July/August that may be related to forest fires. The strongly combustion derived CO shows a single winter maximum and a late summer minimum, albeit with a considerable smaller seasonal swing than the particle data due to its longer atmospheric lifetime. Total volume and even more so total number show a more complex seasonal variation with maxima in winter, spring, and summer. A cluster analysis of back trajectories complemented by local stability information yielded ten clusters with three levels of particle concentration: Low concentrations for the northernmost (Arctic) clusters mid-level concentrations for clusters reaching rapidly west between 55° and 65° latitude, and high concentrations for the cluster reaching southwest via Kazakhstan to the central Russian industrial region.