Diurnal Ranges Research Articles

Ozone concentration at various heights near the surface layer in Shenyang, Northeast China

Ozone pollution has been growing in the recent decade, becoming a critical urban environmental issue in China. However, Shenyang’s near-surface ozone concentration (ground to 100 m altitude) is of grave concern. To obtain the ozone concentration and the corresponding meteorological conditions from 1 October 2018, to 30 September 2019, we built observatory sites at low (≈15 m) and high (≈90 m) layers in Shenyang, northeast China. Then, we analyzed the temporal variation of ozone concentration and discussed the relationship between ozone concentration and the meteorological factors at low and high layers. Compared with the high layer, the ozone concentration in the low layer is chartered with an earlier peak and higher diurnal range. The ozone concentration in all seasons first peaked at a low-layer height, in early in winter (15:00) and late summer (17:00). Then, the peak at high-layer height lagged for behind 1–2 h, generally occurring between 17:00 and 19:00. The variations in ozone concentration at low and high layers differed in daytime and nighttime. The diurnal ranges of ozone concentrations at the low layer were higher than those at the high layer in the four seasons examined. Overall, ozone concentration correlated significantly with air temperature, having correlation coefficients of 0.814 (p < 0.05) in the low layer and 0.731 (p < 0.05) in the high layer. Inversely, it showed a weak correlation with relative humidity: 0.310 (p < 0.05) and 0.351 (p < 0.05) in the low and high layers, respectively. Also, the correlation coefficients with wind speed were meager at both layers. Generally, ozone pollution is not severe in Shenyang.

Diurnal Cycles of Synthetic Microwave Sounding Lower-Stratospheric Temperatures from Radio Occultation Observations, Reanalysis, and Model Simulations

Abstract An observationally based global climatology of the temperature diurnal cycle in the lower stratosphere is derived from 11 different satellites with global positioning system–radio occultation (GPS-RO) measurements from 2006 to 2020. Methods used in our analysis allow for accurate characterization of global stratospheric temperature diurnal cycles, even in the high latitudes where the diurnal signal is small but longer time-scale variability is large. A climatology of the synthetic Microwave Sounding Unit (MSU) and Advanced MSU (AMSU) Temperature in the Lower Stratosphere (TLS) is presented to assess the accuracy of diurnal cycle climatologies for the MSU and AMSU TLS observations, which have traditionally been generated by model data. The TLS diurnal ranges are typically less than 0.4 K in all latitude bands and seasons investigated. It is shown that the diurnal range (maximum minus minimum temperature) of TLS is largest over Southern Hemisphere tropical land in the boreal winter season, indicating the important role of deep convection. The range, phase, and seasonality of the TLS diurnal cycle are generally well captured by the WACCM6 simulation and ERA5 dataset. We also present an observationally based diurnal cycle climatology of temperature profiles from 300 to 10 hPa for various latitude bands and seasons and compare the ERA5 data with the observations.

Simulation of Longwave Enhancement in Boreal and Montane Forests

AbstractBoreal forests cover about a fifth of seasonally snow‐covered land over the Northern Hemisphere. Enhancement of longwave radiation beneath coniferous forests has been found to impact the surface energy balance and rates of snowmelt. Although the skill of model‐simulated snowmelt has been shown to be lower for forests than for open areas, model intercomparisons and evaluations of model parameterizations have not yet focused on longwave enhancement. This study uses stand‐scale forcing for the simulation of subcanopy longwave radiation by Community Land Model version 4.5 (CLM4.5) and to drive SNOWPACK, a snow model featuring more complex canopy structure, as a benchmark model for CLM4.5. Simulated subcanopy longwave radiation and longwave enhancement are assessed using measurements from forest stands located within perennially snow‐covered regions. These forest stands, of varying canopy density, cover the range of boreal plant functional types in CLM4.5. CLM4.5 is found to overestimate the diurnal range of subcanopy longwave radiation and longwave enhancement, and simulation errors increase with decreasing cloudiness and increasing vegetation density. Implementation of a parameterization of heat storage by biomass reduces simulation errors but only marginally affects the amplitude of diurnal ranges. These results reaffirm previous findings that simulation of subcanopy longwave radiation can be improved by partitioning the vegetation canopy into two layers. Moreover, this study reveals the variations of simulation errors across meteorological conditions and vegetation density, the latter of which is the most important parameter for longwave enhancement independent of vegetation type.

Understanding Land–Atmosphere–Climate Coupling from the Canadian Prairie Dataset

Analysis of the hourly Canadian Prairie data for the past 60 years has transformed our quantitative understanding of land–atmosphere–cloud coupling. The key reason is that trained observers made hourly estimates of the opaque cloud fraction that obscures the sun, moon, or stars, following the same protocol for 60 years at all stations. These 24 daily estimates of opaque cloud data are of sufficient quality such that they can be calibrated against Baseline Surface Radiation Network data to yield the climatology of the daily short-wave, long-wave, and total cloud forcing (SWCF, LWCF and CF, respectively). This key radiative forcing has not been available previously for climate datasets. Net cloud radiative forcing changes sign from negative in the warm season, to positive in the cold season, when reflective snow reduces the negative SWCF below the positive LWCF. This in turn leads to a large climate discontinuity with snow cover, with a systematic cooling of 10 °C or more with snow cover. In addition, snow cover transforms the coupling between cloud cover and the diurnal range of temperature. In the warm season, maximum temperature increases with decreasing cloud, while minimum temperature barely changes; while in the cold season with snow cover, maximum temperature decreases with decreasing cloud, and minimum temperature decreases even more. In the warm season, the diurnal ranges of temperature, relative humidity, equivalent potential temperature, and the pressure height of the lifting condensation level are all tightly coupled to the opaque cloud cover. Given over 600 station-years of hourly data, we are able to extract, perhaps for the first time, the coupling between the cloud forcing and the warm season imbalance of the diurnal cycle, which changes monotonically from a warming and drying under clear skies to a cooling and moistening under cloudy skies with precipitation. Because we have the daily cloud radiative forcing, which is large, we are able to show that the memory of water storage anomalies, from precipitation and the snowpack, goes back many months. The spring climatology shows the memory of snowfall back through the entire winter, and the memory in summer, goes back to the months of snowmelt. Lagged precipitation anomalies modify the thermodynamic coupling of the diurnal cycle to the cloud forcing, and shift the diurnal cycle of the mixing ratio, which has a double peak. The seasonal extraction of the surface total water storage is a large damping of the interannual variability of precipitation anomalies in the growing season. The large land-use change from summer fallow to intensive cropping, which peaked in the early 1990s, has led to a coupled climate response that has cooled and moistened the growing season, lowering cloud-base, increasing equivalent potential temperature, and increasing precipitation. We show a simplified energy balance of the Prairies during the growing season, and its dependence on reflective cloud.

Annual Climatology of the Diurnal Cycle on the Canadian Prairies

We show the annual climatology of the diurnal cycle, stratified by opaque cloud, using the full hourly resolution of the Canadian Prairie data. The opaque cloud field itself has distinct cold and warm season diurnal climatologies; with a near-sunrise peak of cloud in the cold season and an early afternoon peak in the warm season. There are two primary climate states on the Canadian Prairies, separated by the freezing point of water, because a reflective surface snow cover acts as a climate switch. Both cold and warm season climatologies can be seen in the transition months of November, March and April with a large difference in mean temperature. In the cold season with snow, the diurnal ranges of temperature and relative humidity increase quasi-linearly with decreasing cloud, and increase from December to March with increased solar forcing. The warm season months, April to September, show a homogeneous coupling to the cloud cover, and a diurnal cycle of temperature and humidity that depends only on net longwave. Our improved representation of the diurnal cycle shows that the warm season coupling between diurnal temperature range and net longwave is weakly quadratic through the origin, rather than the linear coupling shown in earlier papers. We calculate the conceptually important 24-h imbalances of temperature and relative humidity (and other thermodynamic variables) as a function of opaque cloud cover. In the warm season under nearly clear skies, there is a warming of +2oC and a drying of -6% over the 24-h cycle, which is about 12% of their diurnal ranges. We summarize results on conserved variable diagrams and explore the impact of surface windspeed on the diurnal cycle in the cold and warm seasons. In all months, the fall in minimum temperature is reduced with increasing windspeed, which reduces the diurnal temperature range. In July and August, there is an increase of afternoon maximum temperature and humidity at low windspeeds, and a corresponding rise in equivalent potential temperature of 4.4K that appears coupled to increased precipitation. However overcast skies are associated with the major rain events and higher windspeeds.

The interrelationship between dengue incidence and diurnal ranges of temperature and humidity in a Sri Lankan city and its potential applications

BackgroundTemperature, humidity, and other weather variables influence dengue transmission. Published studies show how the diurnal fluctuations of temperature around different mean temperatures influence dengue transmission. There are no published studies about the correlation between diurnal range of humidity and dengue transmission.ObjectiveThe goals of this study were to determine the correlation between dengue incidence and diurnal fluctuations of temperature and humidity in the Sri Lankan city of Kandy and to explore the possibilities of using that information for better control of dengue.DesignWe calculated the weekly dengue incidence in Kandy during the period 2003–2012, after collecting data on all of the reported dengue patients and estimated midyear populations. Data on daily maximum and minimum temperatures and night-time and daytime humidity were obtained from two weather stations, averaged, and converted into weekly data. The number of days per week with a diurnal temperature range (DTR) of >10°C and <10°C and the number of days per week with a diurnal humidity range (DHR) of >20 and <15% were calculated. Wavelet time series analysis was performed to determine the correlation between dengue incidence and diurnal ranges of temperature and humidity.ResultsThere were negative correlations between dengue incidence and a DTR >10°C and a DHR >20% with 3.3-week and 4-week lag periods, respectively. Additionally, positive correlations between dengue incidence and a DTR <10°C and a DHR <15% with 3- and 4-week lag periods, respectively, were discovered.ConclusionsThese findings are consistent with the results of previous entomological studies and theoretical models of DTR and dengue transmission correlation. It is important to conduct similar studies on diurnal fluctuations of humidity in the future. We suggest ways and means to use this information for local dengue control and to mitigate the potential effects of the ongoing global reduction of DTR on dengue incidence.

Impact of land use change on the diurnal cycle climate of the Canadian Prairies

AbstractThis paper uses hourly observations from 1953 to 2011 of temperature, relative humidity, and opaque cloud cover from 14 climate stations across the Canadian Prairies to analyze the impact of agricultural land use change on the diurnal cycle climate, represented by the mean temperature and relative humidity and their diurnal ranges. We show the difference between the years 1953–1991 and 1992–2011. The land use changes have been largest in Saskatchewan where 15–20% of the land area has been converted in the past four decades from summer fallow (where the land was left bare for 1 year) to annual cropping. During the growing season from 20 May to 28 August, relative humidity has increased by about 7%. During the first 2 months, 20 May to 19 July, maximum temperatures and the diurnal range of temperature have fallen by 1.2°C and 0.6°C, respectively, cloud cover has increased by about 4%, reducing surface net radiation by 6 W m−2, and precipitation has increased. We use the dry‐downs after precipitation to separate the impact of cloud cover and show the coupling between evapotranspiration and relative humidity. We estimate, using reanalysis data from ERA‐Interim, that increased transpiration from the larger area of cropland has reduced the surface Bowen ratio by 0.14–0.2. For the month on either side of the growing season, cloud cover has fallen slightly; maximum temperatures have increased, increasing the diurnal temperature range and the diurnal range of humidity.

Cloud radiative forcing of the diurnal cycle climate of the Canadian Prairies

This analysis uses 40 years of hourly observations of temperature (T), relative humidity (RH), and opaque cloud cover from 14 climate stations across the Canadian Prairies to analyze the diurnal cycle climate, represented by the mean T and RH and their diurnal ranges. From April to October, when incoming shortwave radiation dominates over longwave cooling, maximum temperature and the diurnal ranges of T and RH increase with decreasing opaque cloud cover, while minimum temperature is almost independent of cloud. During the winter period, both maximum and minimum temperatures fall with decreasing cloud, as longwave cooling dominates over the net shortwave flux, which is reduced by the high solar zenith angle and surface reflection by snow. We relate the daily mean opaque cloud cover to the longwave and shortwave cloud forcing and the effective cloud albedo, using multiyear measurements of downward shortwave and longwave fluxes, and longwave fluxes under clear skies from historical weather reanalysis. We provide quadratic fits to compute effective cloud albedo and net longwave fluxes from opaque cloud cover. During the warm season, the daytime rise of temperature is related to the net radiation, and the nighttime fall is related to the net longwave cooling. The diurnal range of T, RH, and all the net radiative fluxes have a quasi‐linear dependence on the effective cloud albedo. This gives a seasonal climate perspective on the coupled land‐surface system of T, RH, and cloud cover over the Canadian Prairies, and the winter transitions in snowy climates.

Plant drought tolerance assessment for re-vegetation in heterogeneous karst landscapes of southwestern China

A better understanding of plant water relations is needed for evaluating the suitability of plant species to site-specific reforestation programs in the heterogeneous karst landscapes in southwestern China that are characterized by temporary water deficit. During both wet and dry periods, leaf water potentials of 65 plant species from five different growth forms were studied at three representative sites (forest, shrubland and grassland), to compare their adaptive strategies against water stress and assess their suitability for reforestation programs. Herbs showed the highest predawn and midday water potentials and smallest diurnal ranges of water potential values at all the three sites, indicating that they follow water stress avoidance strategies. During the dry period, evergreen shrubs showed low water potentials, the largest diurnal ranges and highest soluble sugar contents. This indicates that they have a tolerance strategy responding to water stress. Deciduous shrubs and trees still showed relatively large diurnal ranges of water potential values and high soluble sugar contents, and did not shed leaves when experiencing the lowest midday water potentials during the dry period. They shed leaves only later in the dry winter period when even more serious drought was experienced. Their strategies seem to include both tolerance and avoidance mechanisms. Evergreen trees revealed relatively low water potentials with smallest diurnal range water potentials at the shrubland site, especially during the dry period, which indicated their weak ability to tolerate severe water stress. Increasing degradation of the vegetation clearly impacts negatively plant water relations. Using the ranges of leaf water potentials, the relative suitability of the plants for reforestation could be evaluated.

On the diurnal ranges of Sea Surface Temperature (SST) in the north Indian Ocean

This paper describes the variability in the diurnal range of SST in the north Indian Ocean using in situ measurements and tests the suitability of simple regression models in estimating the diurnal range. SST measurements obtained from 1556 drifting and 25 moored buoys were used to determine the diurnal range of SSTs. The magnitude of diurnal range of SST was highest in spring and lowest in summer monsoon. Except in spring, nearly 75–80% of the observations reported diurnal range below 0.5°C. The distributions of the magnitudes of diurnal warming across the three basins of north Indian Ocean (Arabian Sea, Bay of Bengal and Equatorial Indian Ocean) were similar except for the differences between the Arabian Sea and the other two basins during November–February (winter monsoon) and May. The magnitude of diurnal warming that depended on the location of temperature sensor below the water level varied with seasons. In spring, the magnitude of diurnal warming diminished drastically with the increase in the depth of temperature sensor. The diurnal range estimated using the drifting buoy data was higher than the diurnal range estimated using moored buoys fitted with temperature sensors at greater depths.A simple regression model based on the peak solar radiation and average wind speed was good enough to estimate the diurnal range of SST at ∼1.0 m in the north Indian Ocean during most of the seasons except under low wind-high solar radiation conditions that occur mostly during spring. The additional information on the rate of precipitation is found to be redundant for the estimation of the magnitude of diurnal warming at those depths.

Home range of the Japanese fluvial sculpin, Cottus pollux, in relation to nocturnal activity patterns

Patterns of space use related to the activity of individual Japanese fluvial sculpins, Cottus pollux, were examined during the non-breeding season, in the upper reaches of the Inabe River, central Japan. Sculpins appeared more frequently at night than in daytime. Among 31 recaptured sculpins, 30 (96.8%) showed nocturnal activity patterns, there being no fish which exhibited an entirely diurnal activity pattern. Of 21 sculpins captured both in daytime and at night, the most common pattern of space use (n = 14, 66.7%) was that in which the nocturnal home range entirely encompassed the diurnal range. Overall, nocturnal home ranges were significantly larger than diurnal ranges. Active sculpins were rarely found on sand-associated substrata in daytime, but were seen more frequently on such substrata at night.

OBSERVED CHANGES IN MAXIMUM AND MINIMUM TEMPERATURES IN TURKEY

The aim of this study is to examine the nature and magnitude of the changes in mean seasonal daily maximum and minimum temperatures and diurnal temperature ranges for all of Turkey, its regions and the 59 stations during the period 1930–1993. Maximum temperatures show significant cooling trends in many stations in summer and autumn. Most of the regional mean maximum temperatures have decreased in all seasons, except spring. None of the observed trends in regions was significant statistically. Mean seasonal minimum temperatures have indicated significant warming trends in many stations in all seasons except winter. Majorities of the regional mean minimum temperatures have also increased markedly in all seasons. Warming trends of spring minimum temperatures were significant over the Black Sea, Aegean and South-eastern Anatolia regions. Spring minimum temperat ures for all of Turkey have shown a significant linear trend, with an increase of +0·145°C per decade. Diurnal temperature ranges have decreased significantly over most of the regions in all seasons, except partly in autumn and in so many stations in all seasons. Most of the decreasing trends in summer were significant at the 1 per cent level. It seems that changes of the diurnal temperature range in spring, summer and autumn were related closely to changes of maximum temperatures. Thus the decrease of the regional mean diurnal range was associated mainly with decreases of maximum temperatures in summer and autumn, and with slightly increased maximum temperatures in spring. Many stations that experienced a significant trend in diurnal ranges had a significant positive serial correlation. Our first results for Ankara have shown no significant trend in the mean monthly cloudiness and monthly cloudiness at 1400 hours local time, except a decrease in May cloudiness at 1400 hours.

OBSERVED CHANGES IN MAXIMUM AND MINIMUM TEMPERATURES IN TURKEY

The aim of this study is to examine the nature and magnitude of the changes in mean seasonal daily maximum and minimum temperatures and diurnal temperature ranges for all of Turkey, its regions and the 59 stations during the period 1930–1993. Maximum temperatures show significant cooling trends in many stations in summer and autumn. Most of the regional mean maximum temperatures have decreased in all seasons, except spring. None of the observed trends in regions was significant statistically. Mean seasonal minimum temperatures have indicated significant warming trends in many stations in all seasons except winter. Majorities of the regional mean minimum temperatures have also increased markedly in all seasons. Warming trends of spring minimum temperatures were significant over the Black Sea, Aegean and South-eastern Anatolia regions. Spring minimum temperat ures for all of Turkey have shown a significant linear trend, with an increase of +0·145°C per decade. Diurnal temperature ranges have decreased significantly over most of the regions in all seasons, except partly in autumn and in so many stations in all seasons. Most of the decreasing trends in summer were significant at the 1 per cent level. It seems that changes of the diurnal temperature range in spring, summer and autumn were related closely to changes of maximum temperatures. Thus the decrease of the regional mean diurnal range was associated mainly with decreases of maximum temperatures in summer and autumn, and with slightly increased maximum temperatures in spring. Many stations that experienced a significant trend in diurnal ranges had a significant positive serial correlation. Our first results for Ankara have shown no significant trend in the mean monthly cloudiness and monthly cloudiness at 1400 hours local time, except a decrease in May cloudiness at 1400 hours.

Comparison of observed seasonal temperature maxima, minima and diurnal range in North America with simulations from three global climate models

Confidence in model projections of climate change requires reasonably realistic simulation of present-day climate (Wilson and Mitchell, 1987; Boer, 1992). Accordingly, we compare surface air temperatures simulated in the control runs of three general circulation models (Canadian Climate Centre, Oregon State University, United Kingdom Meteorological Office) with observations in three regions of the central United States. The models simulate a smaller diurnal surface air temperature range, averaging overall 3.2°C less than observed. Spring maxima are consistently lower in the models by an average of 4.1°C. Although inadequate representation of clouds may contribute to the smaller simulated temperature range, the underlying cause of the differences is unknown. Since increased minima and decreased diurnal ranges are the most widely observed features of surface air temperature over the Northern Hemisphere continents during the last four decades, the discrepancy is a matter of concern for the projection of future greenhouse-gas-induced climate changes and their impacts.

Diurnal and seasonal variations of space charge, electric field and cloud condensation nuclei in the lowest layer of the atmosphere

Diurnal and seasonal variations of space charge, vertical electric field and cloud condensation nuclei in the lowest layers of the atmosphere during winter, pre-monsoon, monsoon and post-monsoon seasons were studied. The curve showing the diurnal variation of space charge exhibited a double oscillation corresponding to that of the electric field during winter and pre-monsoon seasons. Similar features are absent during monsoon and post-monsoon seasons. During pre-monsoon the semi-diurnal components of space charge and electric field are in phase while in winter the semi-diurnal component of space charge occurs 1 h ahead of the electric field component. The mean values and diurnal ranges of both space charge and electric field are high during winter/pre-monsoon and are low during monsoon/post-monsoon seasons. The diurnal range of temperature and concentration of cloud condensation nuclei are positively correlated with space charge and the electric field. The pre-sunrise minimum in the electric field is associated with the characteristics of the F-region of the ionosphere rather than with the ground sunrise time. The variations in the F 2 layer critical frequency ( f 0 F 2 ) are reflected in the diurnal and ter-diurnal components of the surface electric field. The results of the present study support the hypothesis that the increase in the electrosphere potential could be the source of the atmospheric electric sunrise effect (Muir, 1975). DOI: 10.1111/j.2153-3490.1980.tb00950.x

Diurnal and seasonal variations of space charge, electric field and cloud condensation nuclei in the lowest layer of the atmosphere

Diurnal and seasonal variations of space charge, vertical electric field and cloud condensation nuclei in the lowest layers of the atmosphere during winter, pre-monsoon, monsoon and post-monsoon seasons were studied. The curve showing the diurnal variation of space charge exhibited a double oscillation corresponding to that of the electric field during winter and pre-monsoon seasons. Similar features are absent during monsoon and post-monsoon seasons. During pre-monsoon the semi-diurnal components of space charge and electric field are in phase while in winter the semi-diurnal component of space charge occurs 1 h ahead of the electric field component. The mean values and diurnal ranges of both space charge and electric field are high during winter/pre-monsoon and are low during monsoon/post-monsoon seasons. The diurnal range of temperature and concentration of cloud condensation nuclei are positively correlated with space charge and the electric field. The pre-sunrise minimum in the electric field is associated with the characteristics of the F-region of the ionosphere rather than with the ground sunrise time. The variations in the F 2 layer critical frequency ( f 0 F 2 ) are reflected in the diurnal and ter-diurnal components of the surface electric field. The results of the present study support the hypothesis that the increase in the electrosphere potential could be the source of the atmospheric electric sunrise effect (Muir, 1975). DOI: 10.1111/j.2153-3490.1980.tb00950.x

THE APERIODIC DIURNAL RANGE OF TEMPERATURE OVER THE NORTH ATLANTIC OCEAN

Abstract Frequency distributions of aperiodic diurnal ranges of temperatures at 9 of the North Atlantic Ocean Vessel Stations are examined. It is found that the means, disperions, and asymmetries of these distributions are largest in winter and smallest in summer. It is also found that the aperiodic diurnal range exceeds the periodic diurnal range on virtually all winter days and on the great majority of summer days.

Effect of Variable Temperature Environments on Egg Development of Three Species of Fruit Flies1

Eggs of the oriental fruit fly, Dacus dorsalis Hendel, the melon fly, Dacus cucurbitae Coq., and the Mediterranean fruit fly, Ceratitis capitata (Wied.) were incubated under variable temperatures in automatically controlled, air-conditioned bioclimatic chambers. Idealized temperature patterns, with fixed periodicities and diurnal ranges, and natural temperature patterns, characteristic of many United States localities, were studied; the results of both types of thermal environments, which were closely alike, were compared with constant temperature results previously reported. Only at medial thermal levels (65°–85° F.) do egg development rates under regularly fluctuating temperatures agree closely with those at constant temperatures; at these levels, differences in the diurnal temperature range cause little or no change in rates. Below this medial zone, under variable temperatures there is an acceleration, and in the upper thermal levels a deceleration of development relative to that resulting from constant-temperature exposures, and the greater the diurnal variation, the greater are these effects. Exposures at the lower levels temperatures near or even below the constant temperature threshhold; in several cases completed development occurred after exposure to mean temperatures several degrees below that threshhold. Mean temperatures at high-level exposures never exceeded the constant-temperature upper developmental limit. Swiftest egg development under fluctuating temperature conditions occurred at mean temperatures 5 to 10 degrees below the temperature for most rapid growth under constant conditions; this maximum development rate was somewhat less under fluctuating conditions than when temperatures were held constant. When developmental rates for the egg stage of these flies are plotted against means of the fluctuating temperatures encountered during exposure, the resulting curves, though exhibiting some slight sigmoidal character at the extremities, approach rather closely a rectilinear relation. This is in contrast to the much more pronounced sigmoidal relationship of the corresponding curves noted in constant temperature studies.

Note on a simple measure of the Earth's daily magnetic activity

In a timely paper1 for the Rome meeting of the International Section of Terrestrial Magnetism and Electricity, Dr. G. van Dijk, of the De Bilt Observatory, makes a very desirable comparison, chiefly for the year 1915, of measures of terrestrial magnetic activity proposed by various investigators. For the various measures, designated below, the following symbols are used here: D, magnetic declination; H, horizontal intensity; Z, vertical intensity; R, absolute diurnal range, or difference between extreme daily values of element considered; and A, diurnal range of hourly values (mean value over 60‐minute interval).If at any observatory the diurnal ranges of D and H are not available, then those of the rectangular components X and Y are to be used. In the second, third, and fourth measures the D‐range is to be expressed in gammas, namely, H RD

Societies and Academies

LONDON. Royal Society, March 14.-Sir J. J. Thomson, president, in the chair.-A. W. Conway: An expansion of the point-potential. The general solution of the equation C2v2^=^ which is infinite at: the origin, is of the form f(Ct±r)/r. This is infinite to the first degree. Referred to a different origin, a known expansion gives the series SYwUn, where Y? is a spherical harmonic and Un is a certain function of t and of the distance to the new origin. This is a generalisation of the Legendre expansion of the inverse distance. In the paper the potential scale or vector of a moving point-charge is expanded in a similar series of spherical harmonics, the only restriction on the motions of the point-charge and of the origin being that the speed of the former must be less than that of light.-E. G. Bilham: The lunar and solar diurnal variations of water-level in a well at Kew Observatory, Richmond. The mean solar and lunar diurnal inequalities have been computed from two-hourly measurements of the Kew Observatory water-level records over a period of two years. Results are given for each month, for the year, and for groups of months, representing high, intermediate, and low levels. Both the lunar and solar diurnal ranges are found to be largely dependent on the level of the water, high levels being associated with large diurnal range. In a paper recently communicated to the society it was shown that a similar relation exists between the mean level and the sensitiveness to the effects of barometric pressure. There are well-marked lunar and solar semi-diurnal oscillations throughout the year, the amplitude varying with the level in a manner similar to the diurnal range. In both cases the phase also varies with the level, the effect being most pronounced in the lunar results. The times of occurrence of the maxima become later as the water-level falls. In comparison with the total oscillations in the neighbouring River Thames, the well shows larger solar diurnal movements than were to be anticipated from the magnitude of the lunar oscillations. If, however, allowance is made for the effects of the solar diurnal variation of barometric pressure, the residual effects attributed to the solar tides are of the expected order of magnitude.