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Topic: Seasonal lag

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	Seasonal lag - Wikipedia, the free encyclopedia
		Seasonal lag is the phenomenon whereby the date of maximum average air temperature at a geographical location on a planet is delayed until some time after the date of maximum insolation.
		Earth's seasonal lag is largely caused by the presence of large amounts of water, which has a high latent heat of freezing and of condensation.
		Mars and Venus on the other hand have negligible seasonal lag of no more than a few days, and the same would be expected of Mercury since it has no atmosphere.
	en.wikipedia.org /wiki/Seasonal_lag (293 words)

	Executive Summary (Site not responding. Last check: 2007-11-07)
		Summer season data have a greater relative contribution of long-term and short-term components because the seasonal component is reduced by about half.
		Seasonal ozone in California and Florida exhibits strong semi-annual patterns peaking in the spring and fall.
		Because of the high spatial correlation among seasonal components, for example, it is possible to precisely estimate the baseline of unmonitored locations 200 miles distant (Fig.
	capita.wustl.edu /otag/Reports/StatChar/results.htm (1957 words)

	CalendarHome.com - Summer - Calendar Encyclopedia
		Summer is a season, defined by convention in meteorology as the whole months of June, July, and August, in the Northern hemisphere, and the whole months of December, January, and February, in the Southern hemisphere.
		Summer is commonly viewed as the season with the longest (and warmest) days of the year, in which the daylight predominates, through varying degrees.
		However, due to the phenomenon of seasonal lag, the "meteorological" start of the season precedes, by about three weeks, the start of the "astronomical" season.
	encyclopedia.calendarhome.com /Summer.htm (472 words)

	Research - Valley Fever, Coccidioidomycosis, Fungal
		Onset-diagnosis lags had a mean of 12.6, a median of 11.5, a standard deviation of 5.9, a minimum of 2, and a maximum of 32 days; onset-report lags had respective values of 43.0, 44.0, 19.1, 8, and 99 days.
		Seasons were defined by monthly sequences that captured the predominant seasonal maxima and minima for each variable.
		Stepwise regression of the 1992-2003 seasonal data was used to model coccidioidomycosis rates from concurrent PM (hypothetically related to spore dispersion and therefore exposure) and concurrent and lagged antecedent precipitation (hypothetically related to fungal growth).
	www.valley-fever.org /valley_fever_org_research.html (4117 words)

	[No title]
		The seasonal lag used for the seasonal parameters is usually determined during the identification phase and must be explicitly specified.
		In plots of the series, the distinguishing characteristic between these two types of seasonal components is that in the additive case, the series shows steady seasonal fluctuations, regardless of the overall level of the series; in the multiplicative case, the size of the seasonal fluctuations vary, depending on the overall level of the series.
		If it is zero, then the seasonal component for a particular point in time is predicted to be identical to the predicted seasonal component for the respective time during the previous seasonal cycle, which in turn is predicted to be identical to that from the previous cycle, and so on.
	uregina.ca /~chowsl/webook/sttimser.html (13556 words)

	Lecture 3 outline: Working with seasonal data (Site not responding. Last check: 2007-11-07)
		Seasonal indices can be estimated by averaging the seasonal variations (in percentage terms) that were observed in the past.
		For example, when you seasonally adjust monthly data, you are estimating 12 seasonal indices along with whatever other parameters the model may have.
		The seasonal indices do not show up on the reports generated in the Forecasting procedure, so it is easy to forget that they are there.
	www.duke.edu /~rnau/411l397.htm (1182 words)

	SAS/ETS Examples -- Forecasting a Seasonal ARMA Process
		For multiplicative MA processes, there are small spikes in the ACF plot q lags before and after the seasonal lag, where q is the number of nonseasonal MA parameters necessary to model the data.
		An additive MA process typically has small spikes q lags before the seasonal lag, where q is the number of nonseasonal MA parameters necessary to model the data.
		The lack of a large spike at lag 24 indicates that the series is stationary at the seasonal level.
	support.sas.com /rnd/app/examples/ets/sarma (1138 words)

	[No title]
		Seasonally * adjusted.) graph 1 # rawc end SET c = LOG(rawc(t)) - LOG(rawc(t-1)) * We will work with the first differences of * the natural logarithm of consumption (i.e., * approximate consumption growth) * COMPUTE start = 1959:2 * This statement defines the date when our * historical data begins.
		This is because the seasonal span here * is 12 which implies that lag 24 is just the second * seasonal lag.
		Since the largest AR lag is 36, * when comparing models we estimate each one treating * the first 36 observations as pre-sample.
	www.uncg.edu /eco/pmbearse/eco648/lab5.rtw (1386 words)

	Seasonal ARIMA models
		In identifying a seasonal model, the first step is to determine whether or not a seasonal difference is needed, in addition to or perhaps instead of a non-seasonal difference.
		If the seasonal pattern is both strong and stable over time (e.g., high in the Summer and low in the Winter, or vice versa), then you probably should use a seasonal difference regardless of whether you use a non-seasonal difference, since this will prevent the seasonal pattern from "dying out" in the long-term forecasts.
		The additional term on the right-hand-side is a multiple of the seasonal difference observed in the last month, which has the effect of correcting the forecast for the effect of an unusually "good" or "bad" year.
	www.duke.edu /~rnau/seasarim.htm (2377 words)

	Oracle Data Mining and Analytics: Time Series Forecasting - Part 1
		The seasonal index series, which is the seasonal effect for each period.
		A value greater than one represents a seasonal increase in the data for that period, and a value less than one is a seasonal decrease in the data
		These inputs are called lagged variables and can be easily computed using the SQL LAG analytic function.
	oracledmt.blogspot.com /2006/01/time-series-forecasting-part-1_23.html (1594 words)

	Chapter 1 of Steven R. Hare's Dissertation
		The seasonal mean field that was subtracted from each of the yearly seasonal maps of spring SST is illustrated in Figure 1.3.
		The lag 2 and lag 3 coefficients both appear to be nearly significant as they are approximately twice the value of their respective standard errors.
		The SLP lag 1 coefficient was approximately 0.22.
	www.iphc.washington.edu /Staff/hare/html/diss/chapter1/chap1.html (15361 words)

	Melatonin
		In an artificially synthesized form, melatonin is available as a preventative or a treatment for jet-lag, seasonal affective disorder (SAD), and certain types of depression.
		Called `jet-lag' when it occurs after crossing more than two time zones in a plane, this syndrome can also be caused by working rotating shifts and by experiencing other disruptions to a normal sleep/wake cycle.
		Some people with "seasonal affective disorder" (SAD) experience this syndrome when the low sunlight levels at certain times of the year (winter in northern areas) are not sufficient for their pineal glands to decrease melatonin production to normal low daytime levels.
	www.betterhealthintl.com /articles-melatonin.html (575 words)

	6.4.4.6.2. Model Identification for the CO₂ Concentrations Data
		Since this is monthly data, we would typically include either a lag 12 seasonal autoregressive and/or moving average term.
		To help identify the non-seasonal components, we will take a seasonal difference of 12 and generate the autocorrelation plot on the seasonally differenced data.
		The lag 12 is also significant, indicating some remaining seasonality.
	www.itl.nist.gov /div898/handbook/pmc/section4/pmc4462.htm (338 words)

	Seasonal Affective Disorder Learning Centre (Site not responding. Last check: 2007-11-07)
		Jet lag, or dysrhythmia, occurs when the body clock is not synchronized with an air traveler's new time zone, causing a disruption of more than 50 physiological and psychological rhythms.
		The common symptoms of Jet Lag are fatigue, poor concentration, trouble sleeping, irritability, minor depression, altered estimation of time and distance, and digestive problems.
		Symptoms of Jet Lag occur due to an upset of the human 'body clock', caused by a change in a normal sleeping and waking schedule.
	www.allergymatters.com /test/alpha/acatalog/sad_learning_Centre.html (2160 words)

	[No title]
		The lag is returned and plotted in units of time, and not numbers of observations.
		This should be an object of class \code{"ts"} with a frequency greater than one.} \item{s.window}{either the character string \code{"periodic"} or the span (in lags) of the loess window for seasonal extraction, which should be odd.
		Should be zero or one.} \item{l.window}{the span (in lags) of the loess window of the low-pass filter used for each subseries.
	osiris.sunderland.ac.uk /~cs0pdu/pub/R/library/ts/man/ts.Rd (1919 words)

	Climate Change and Salmon Production in the Northeast Pacific Ocean
		The subscript P identifies the presence of a seasonal component, and all coefficients other than that of the seasonal lag are set equal to 0.
		The subscript Q identifies the presence of a seasonal component, and all coefficients other than that of the seasonal lag are set equal to 0.
		The lag 1 AR term, which had decreased in significance from the no intervention to the one-intervention model, dropped out of the model and a lag 3 AR term was added.
	www.iphc.washington.edu /Staff/hare/html/papers/hare-francis/harefran.html (8973 words)

	seasonal demand - Hutchinson encyclopedia article about seasonal demand (Site not responding. Last check: 2007-11-07)
		Seasonal demand poses problems for businesses because they have to build up stocks for sale during the period of peak demand.
		Seasonal Efficiency of Domestic Boilers in the UK
		This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional.
	encyclopedia.farlex.com /seasonal+demand (153 words)

	COS - Eye Facts - Seasonal depression, jet lag and light therapy (Site not responding. Last check: 2007-11-07)
		As well as sending images to the brain, the eyes also tell our pineal gland, a small pea-sized gland located in the brain, when the day is over.
		Doctors have learned to treat this seasonal depression and jet lag by using a simple device called a light box.
		Because the timing, intensity and duration of the light all play a role in the treatment of each individual case, it is important to stress that the light therapy must be administered by a medical doctor or therapist.
	www.eyesite.ca /english/public-information/eye-facts/seasonal.htm (234 words)

	V72 - 5-methoxy-N-acetyltryptamine - Melatonin
		Melatonin is the principal hormone produced by the pineal gland.
		Melatonin is under investigation as a treatment for a number of conditions, including jet-lag, seasonal affective disorder (SAD), depression, and cancer.
		It has been studied for the treatment of cancer, immune disorders, cardiovascular diseases, depression, seasonal affective disorder, and sexual dysfunction; no apparent benefit in these has been found.
	www.v72.org /melatonin.htm (495 words)

	Melatonin, the Miracle Hormone
		Melatonin is under investigation as a treatment for a number of conditions, including jet lag, seasonal affective disorder (SAD), depression, and cancer.
		Jet lag is characterised by fatigue, early awakening or insomnia, headache, fuzzy thinking, irritability, constipation, and reduced immunity.
		The ability of melatonin to alleviate jet lag was demonstrated in a study of 17 subjects flying from San Francisco to London (eight time zones away).
	optimalhealth.cia.com.au /melatonin1.html (2242 words)

	Seasonal Affective Disorder: Winter Depression
		This condition, known as Seasonal Affective Disorder (SAD) may affect over 10 million Americans while the milder, "Winter Blues" may affect a larger number of individuals.
		In the cases of jet lag or shift work, the individual does not have a disorder, but is reacting to externally induced changes in the sleep-wake cycle.
		Individuals whose PMS was worse in the winter responded better to light therapy than individuals with PMS without a seasonal variation.
	www.ncpamd.com /seasonal.htm (2312 words)

	We’re getting warmer ... sort of - January 13, 2006
		What happens instead is a situation known as "seasonal lag." As the name would suggest, there is something that tends not to keep up with the seasons.
		The human version of seasonal lag shows up in lots of ways.
		Just as the daily seasonal lag is a mini version of what happens during the year, the course of each individual life is a mini version of the unfolding history of our species.
	www.mailtribune.com /archive/2006/0113/life/stories/07life.htm (784 words)

	[No title] (Site not responding. Last check: 2007-11-07)
		The first lead of this * series (that is, the series created by taking the data for the * next time period into the future) is November, the second lead * is October, etc. The lag field seasonal{0 to -11} (in RATS, the * -lags are leads) covers all 12 dummies.
		* seasonal seasons * * The extra parameters on the linreg (after the sample range) * are for series for the residuals and for the coefficients.
		The * coefficients are saved this way only in a very limited number * of situations (such as this one) where they (in whole or in * part) form an interesting sequence.
	www.estima.com /procs/diebold/diebp109.prg (286 words)

	Mailgate: sci.stat.math: Re: time series forecasting (Site not responding. Last check: 2007-11-07)
		If you test 20 lags of a random series at the 5 % level > you can expect to get 1 spurious (incorrect) lag on average.
		AUTOBOX/FREEFORE as a matter of course disallows "silly lags" such as 8 periods and does not "fit" them but still reports their significance.
		I think your suggestion to use the first lag and > a seasonal lag is excellent.
	mailgate.supereva.it /sci/sci.stat.math/msg09972.html (971 words)

	The Daily News Online (Site not responding. Last check: 2007-11-07)
		Online sales, which are expected to increase 20 percent to 26 percent this holiday season, are not included in ShopperTrak's sales figures.
		Another factor that probably dampened sales over the weekend is that the season is two days longer, tempting shoppers to delay their buying even later to get the better deals, according to Scott Krugman, a National Retail Federation spokesman.
		Wal-Mart, which had stepped up discounting after a disappointing start to the holiday season, reported on Saturday an uptick in general merchandise sales the week that ended Friday, noting that sales of winter merchandise improved.
	www.tdn.com /articles/2004/12/21/biz/news01.txt (599 words)

	Mailgate: sci.stat.math: Re: time series forecasting (Site not responding. Last check: 2007-11-07)
		Furthermore, if you test the significance of many lags it is very easy to get spurious results, i.e.
		If you test 20 lags of a random series at the 5 % level you can expect to get 1 spurious (incorrect) lag on average.
		I think your suggestion to use the first lag and a seasonal lag is excellent.
	mailgate.supereva.it /sci/sci.stat.math/msg09958.html (732 words)

	Salk Institute for Biological Studies (Site not responding. Last check: 2007-11-07)
		The finding brings closer to reality medications to treat so-called circadian disorders such as severe jet lag and seasonal depression, as well as improve the lives of shift workers.
		In a bizarre twist, a GNF team led by Satchin Panda, now an assistant professor at the Salk Institute, and Tim Jegla, a group leader at GNF, has shown that the photosensory system that resets the biological clock in people works in the same way as the visual systems of lower animals such as flies.
		When time zones or seasons change, a light sensor in our eyes resets the clock to the new light:dark regime, a process called photoentrainment.
	www.salk.edu /news/releases/details.php?id=117 (764 words)

	ARIMA: Guided tour
		Thus, the p in "ARMA(p,q)" is the maximum lag of the AR part, and q is the maximum lag of the MA part.
		The coefficients a(1,i) are the non-zero coefficients of the non-seasonal AR lag polynomial, and the coefficients c(1,i) are the non-zero coefficients of the seasonal AR lag polynomial.
		Similarly, the coefficients a(2,i) are the non-zero coefficients of the non-seasonal MA lag polynomial, and the coefficients c(2,i) are the non-zero coefficients of the seasonal MA lag polynomial.
	econ.la.psu.edu /~hbierens/EasyRegTours/ARIMA.HTM (1423 words)

	Lecture 5
		This strategy is behind the use of using melatonin to treat ‘jet lag’ or ‘seasonal affective disorders where there is an imbalance in brain serotonin levels due to disruptions in our day-night light-cycles.
		In the first instance, jet lag creates a situation where day is night, and night is day which in effect disrupts one of our biological cycles or rhythms; in the second instance, our biological rhythm is disrupted in the winter time when the nights are long and the days are much shorter.
		In the cases of disorientation, sleepiness, and sometimes the depression associated with seasonal affected disorders (and jet lag), there is usually a positive association of the aforementioned symptoms with levels of serotonin in the brain.
	www.biology.buffalo.edu /courses/bio130/lectures/Lecture5.html (2252 words)

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