E' da circa un mesetto che non aggiorno più il blog. Questo non perchè il mio interesse sulle tematiche trattate (in particolar modo la questione delle scie chimiche) sia improvvisamente scemato ma all'opposto ho dedicato gran parte del poco tempo libero a disposizione per realizzare un progettino che mi passava per la testa da un bel pò di tempo: uno strumento per determinare numericamente la temperatura critica per la formazione delle scie di condensazione. Temperatura critica intesa come quella temperatura massima (in funzione di una data pressione atmosferica, umidità relativa e tipologia di motore) sotto la quale gli aerei possono generare le contrails.L'idea è nata dopo aver letto,riletto e straletto l'articolo APPLEMAN 2.0 realizzato da Cuorenero sul suo blog.Le difficoltà incontrate sono state molteplici, la prima in assoluto interpretare i formuloni proposti nelle varie pubblicazioni di riferimento. In particolar modo tra i metodi di forecasting "attuali" mi sono focalizzato su quello realizzato da Mark Schrader nella fine del 1996 (datazione dell'articolo utilizzato) che risulta essere almeno fino a tale data il metodo previsionale ufficiale utilizzato dall'AIR FORCE GLOBAL WEATHER CENTER (AFGWC).Sostanzialmente questo metodo previsionale nasce dalle basi fornite da Appleman negli anni '50 con la variante della presenza di un CONTRAIL FACTOR variabile a seconda della tipologia di motore. Questo coefficente è calcolato in base alla massa di vapore released by waste water, the heat of the air at a given constant pressure and the total energy released by the engine.
There are three types of aircraft engines that can produce contrails contrail which correspond to three different factors that are changing the critical temperature for a given atmospheric pressure and relative humidity:
The contrail factor constant sull'appleman originally used instead equal to 0.0336 g kg ^ (-1) K ^ (-1).
The lower value is for the engines "did not pass" and a maximum of the "high bypass", the highest value of contrail factor is thus more critical temperature and consequently the possibility of formation of contrails at lower altitudes and its the last generation aircraft.
Same weather conditions
A340 (high-pass) with the wake and B707 (low pass) without wake
Once I clarified a bit on the theoretical ideas are passed the phase realizzazione.Per do this after 15 years I put the clothes of a simple executable program generated stand alone in the DOS which in the incorporation of pressure, relative humidity, ambient temperature and produces as output the contrail factor calculated critical temperature and, by comparison with the ambient temperature, an indication of whether or not there are conditions for the formation of contrails. The first release of the program that I simply called "contrail" can be downloaded HERE , shortly release a version in English. The data of temperature, barometric pressure and relative humidity can be deduced from soundings at the site of present day ' University of Wyoming . On the goodness of the data provided by the probes (model VAISALA RS92) should make a separate discussion, particularly on the values \u200b\u200bof relative humidity, as shown by recent publications, suffer from an error in measurement caused by daytime solar radiation leads to a significant underestimation. Recently came out of the algorithms based on atmospheric pressure and solar zenith angle of to correct these discrepancies between the expected and measured RH. Specifies that the released version does not contain any correction algorithm for different data entered in the face of new insights on the various publications and I hope suggestions by users do not rule out, on time necessari ,il rilascio di nuove versioni.
Spero sia di gradimento e di utilità sopratutto per coloro che ancora credono che la formazione delle scie di condensazione sia un fenomeno rarissimo e condizionato esclusivamente al famoso 70% di umidità relativa.
Buon utilizzo!
Download:
CONTRAIL FORECASTING using SCHRADER method
Referenze:
Mark L. Schrader, "Calculations of Aircraft Contrail Formation Critical Temperatures" (1996)
Radicedimenouno, Appleman 2.0
Ringraziamenti:
Cuorenero per disponibilità
Cieliazzurri per il beta testing
NOT BYPASS (CF = 0.0300) propeller engines
LOW BYPASS (CF = 0.0340) jet engines of the first and second generation characteristic of the aircraft built in the 70s (eg MD80)
HIGH BYPASS (CF = 0.039) next-generation jet engines present on all modern commercial aircraft and military transport
LOW BYPASS (CF = 0.0340) jet engines of the first and second generation characteristic of the aircraft built in the 70s (eg MD80)
HIGH BYPASS (CF = 0.039) next-generation jet engines present on all modern commercial aircraft and military transport
The contrail factor constant sull'appleman originally used instead equal to 0.0336 g kg ^ (-1) K ^ (-1).
The lower value is for the engines "did not pass" and a maximum of the "high bypass", the highest value of contrail factor is thus more critical temperature and consequently the possibility of formation of contrails at lower altitudes and its the last generation aircraft.
Same weather conditions A340 (high-pass) with the wake and B707 (low pass) without wake
Once I clarified a bit on the theoretical ideas are passed the phase realizzazione.Per do this after 15 years I put the clothes of a simple executable program generated stand alone in the DOS which in the incorporation of pressure, relative humidity, ambient temperature and produces as output the contrail factor calculated critical temperature and, by comparison with the ambient temperature, an indication of whether or not there are conditions for the formation of contrails. The first release of the program that I simply called "contrail" can be downloaded HERE , shortly release a version in English. The data of temperature, barometric pressure and relative humidity can be deduced from soundings at the site of present day ' University of Wyoming . On the goodness of the data provided by the probes (model VAISALA RS92) should make a separate discussion, particularly on the values \u200b\u200bof relative humidity, as shown by recent publications, suffer from an error in measurement caused by daytime solar radiation leads to a significant underestimation. Recently came out of the algorithms based on atmospheric pressure and solar zenith angle of to correct these discrepancies between the expected and measured RH. Specifies that the released version does not contain any correction algorithm for different data entered in the face of new insights on the various publications and I hope suggestions by users do not rule out, on time necessari ,il rilascio di nuove versioni.
Spero sia di gradimento e di utilità sopratutto per coloro che ancora credono che la formazione delle scie di condensazione sia un fenomeno rarissimo e condizionato esclusivamente al famoso 70% di umidità relativa.
Buon utilizzo!
Download:
CONTRAIL FORECASTING using SCHRADER method
Referenze:
Mark L. Schrader, "Calculations of Aircraft Contrail Formation Critical Temperatures" (1996)
Radicedimenouno, Appleman 2.0
Ringraziamenti:
Cuorenero per disponibilità
Cieliazzurri per il beta testing
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